Method and apparatus for transmitting uplink signal in wireless communication system

ABSTRACT

The present invention relates to a wireless communication system and, more specifically, to a method and an apparatus for transmitting an uplink signal. The method for transmitting an uplink signal from a terminal in a wireless communication system, according to one embodiment of the present invention, comprises the steps of: receiving configuration information about candidates in a parameter set for a reference signal for physical uplink shared channel (PUSCH) modulation; receiving information indicating a specific set among the candidates in the parameter set; and generating a sequence of the reference signal using the specific set and transmitting the generated reference signal to a base station, wherein the information indicating the specific set may have a maximum value of the minimum distance between a circular shift index of the reference signal generated by a terminal using the specific set and a circular shift index of a reference signal generated by another terminal using the specific set.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2013/001326, filed on Feb. 20, 2013,which claims the benefit of U.S. Provisional Application Ser. Nos.61/600,999, filed on Feb. 20, 2012, 61/606,466, filed on Mar. 4, 2012,61/606,983, filed on Mar. 5, 2012, 61/619,408, filed on Apr. 2, 2012,and 61/646,353, filed on May 13, 2012, the contents of which are allhereby incorporated by reference herein in their entirety.

TECHNICAL FIELD

The present description relates to wireless communication, and morespecifically, to a method and apparatus for transmitting an uplinksignal.

BACKGROUND ART

To satisfy increasing data throughput in a wireless communicationsystem, MIMO, multi-base station cooperation technology, etc. forincreasing throughput of data transmitted in a limited frequency bandhave been developed.

An enhanced wireless communication system that supports multi-basestation cooperative communication through which a plurality of eNBscommunicate with user equipments (UEs) using the same time-frequencyresource can provide increased data throughput, compared to aconventional wireless communication system in which one eNB communicateswith UEs. eNBs participating in cooperative communication may bereferred to as cells, antenna ports, antenna port groups, RRHs (RemoteRadio Heads), transport points, reception points, access points, etc.

DISCLOSURE Technical Problem

With the introduction of new wireless communication technology, thenumber of UEs to which an eNB needs to provide a service in apredetermined resource region increases and the quantity of data andcontrol information transmitted/received between the eNBs and UEs towhich the eNB provides the service also increases. Since the quantity ofradio resource that can be used for the eNB to communicate with the UEsis finite, there is a need for a new method by which the ENB efficientlytransmits/receives uplink/downlink data and/or uplink/downlink controlinformation to/from UEs using finite radio resource.

An object of the present invention devised to solve the problem lies ona new method for transmitting an uplink reference signal to supportenhanced uplink transmission and a method for successfully receiving theuplink reference signal at an uplink signal receiver.

The technical problems solved by the present invention are not limitedto the above technical problems and those skilled in the art mayunderstand other technical problems from the following description.

Technical Solution

The object of the present invention can be achieved by providing amethod for transmitting, by a UE, an uplink signal in a wireless accesssystem, including: receiving configuration information regardingparameter set candidates related to a reference signal for demodulationof a physical uplink shared channel (PUSCH); receiving informationindicating a specific parameter set from among the parameter setcandidates; and generating a sequence of the reference signal using thespecific parameter set and transmitting the generated reference signalsequence to a base station (BS), wherein the information indicating thespecific parameter set further indicates one of a plurality of cyclicshift (CS) indices, and the CS indices have values maximizing a minimumdistance between CS indices.

In another aspect of the present invention, provided herein is a UE fortransmitting an uplink signal, including: a receiver; a transmitter; anda processor, wherein the processor is configured to receiveconfiguration information about parameter set candidates related to areference signal for demodulation of a PUSCH using the receiver, toreceive information indicating a specific parameter set from among theparameter set candidates using the receiver, to generate a sequence ofthe DMRS using the specific parameter set and to transmit the generatedDMRS sequence to a BS, wherein the information indicating the specificparameter set has a value maximizing a minimum distance between a CSindex of the reference signal generated by the UE using the specificparameter set and a CS index of a reference signal generated by anotherUE using the specific parameter set.

The following is commonly applicable to the aforementioned embodimentsof the present invention.

The parameter set candidates may include parameter sets includingphysical cell IDs (PCIs).

The information indicating the specific parameter set may be dynamicallysignaled using a predetermined field of uplink-related downlink controlinformation (DCI).

The predetermined field may be a demodulation reference signal (DMRS)cyclic shift (CS) and orthogonal cover code (OCC) field.

The DMRS CS and OCC field may indicate the specific parameter settogether with a second parameter n_(DMRS) ⁽²⁾ used to determine a CSindex with respect to the reference signal.

The predetermined field may be a resource allocation type (RAT)indication field.

Whether the predetermined field signals the information indicating thespecific parameter set may be set by a higher layer.

The information about the parameter set candidates may beUE-specifically or UE-group-specifically signaled by a higher layer.

The specific parameter set may be independently set per layer of the UE.

The UE may be paired with another UE for multiple user MIMO (MU-MIMO).

The parameter set may include at least one of a virtual cell ID (VCI)used for generation of the reference signal, an offset parameter Δ_(ss)between a sequence shift pattern of a physical uplink shared channel(PUCCH) DMRS and a sequence shift pattern of the PUSCH DMRS, an initialvalue c_(init) ^(CSH) of a pseudo-random sequence which determines acyclic shift hopping pattern of the PUSCH DMRS, a first parametern_(DMRS) ⁽¹⁾ used to determine a CS index with respect to the referencesignal, a second parameter n_(DMRS) ⁽²⁾ used to determine the CS indexwith respect to the reference signal, and an offset Δn_(DMRS) used todetermine the CS index.

The reference signal may be transmitted on an SC-FDMA (Single CarrierFrequency Division Multiple Access) symbol in a slot in which the PUSCHis transmitted.

The technical problems solved by the present invention are not limitedto the above technical problems and those skilled in the art mayunderstand other technical problems from the following description.

Advantageous Effects

The present invention can provide a new method for transmitting anuplink reference signal to support enhanced uplink transmission and amethod for successfully receiving the uplink reference signal at anuplink signal receiver.

The effects of the present invention are not limited to theabove-described effects and other effects which are not described hereinwill become apparent to those skilled in the art from the followingdescription.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the inventionand together with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a radio frame structure;

FIG. 2 illustrates a resource grid;

FIG. 3 illustrates a downlink subframe structure;

FIG. 4 illustrates an uplink subframe structure;

FIG. 5 illustrates a downlink reference signal;

FIGS. 6 to 10 illustrate UCI transmission using PUCCH (Physical UplinkControl Channel) format 1 series, PUCCH format 2 series and PUCCH format3 series;

FIG. 11 illustrates multiplexing of uplink control information anduplink data in a PUSCH (Physical Uplink Shared Channel) region;

FIG. 12 illustrates an exemplary UL CoMP operation;

FIG. 13 is a flowchart illustrating an uplink reference signaltransmission method according to an embodiment of the present invention;and

FIG. 14 shows configurations of an eNB and a UE according to anembodiment of the present invention.

BEST MODE

Embodiments described hereinbelow are combinations of elements andfeatures of the present invention. The elements or features may beconsidered selective unless otherwise mentioned. Each element or featuremay be practiced without being combined with other elements or features.Further, an embodiment of the present invention may be constructed bycombining parts of the elements and/or features. Operation ordersdescribed in embodiments of the present invention may be rearranged.Some constructions of any one embodiment may be included in anotherembodiment and may be replaced with corresponding constructions ofanother embodiment.

In the embodiments of the present invention, a description is made,centering on a data transmission and reception relationship between abase station (BS) and a User Equipment (UE). The BS is a terminal nodeof a network, which communicates directly with a UE. In some cases, aspecific operation described as performed by the BS may be performed byan upper node of the BS.

Namely, it is apparent that, in a network comprised of a plurality ofnetwork nodes including a BS, various operations performed forcommunication with a UE may be performed by the BS, or network nodesother than the BS. The term ‘BS’ may be replaced with the term ‘fixedstation’, ‘Node B’, ‘evolved Node B (eNode B or eNB)’, ‘Access Point(AP)’, etc. The term ‘UE’ may be replaced with the term ‘terminal’,‘Mobile Station (MS)’, ‘Mobile Subscriber Station (MSS)’, ‘SubscriberStation (SS)’, etc.

Specific terms used for the embodiments of the present invention areprovided to aid in understanding of the present invention. Thesespecific terms may be replaced with other terms within the scope andspirit of the present invention.

In some cases, to prevent the concept of the present invention frombeing ambiguous, structures and apparatuses of the known art will beomitted, or will be shown in the form of a block diagram based on mainfunctions of each structure and apparatus. Also, wherever possible, thesame reference numbers will be used throughout the drawings and thespecification to refer to the same or like parts.

The embodiments of the present invention can be supported by standarddocuments disclosed for at least one of wireless access systems,Institute of Electrical and Electronics Engineers (IEEE) 802, 3^(rd)Generation Partnership Project (3GPP), 3GPP Long Term Evolution (3GPPLTE), LTE-Advanced (LTE-A), and 3GPP2. Steps or parts that are notdescribed to clarify the technical features of the present invention canbe supported by those documents. Further, all terms as set forth hereincan be explained by the standard documents.

Techniques described herein can be used in various wireless accesssystems such as Code Division Multiple Access (CDMA), Frequency DivisionMultiple Access (FDMA), Time Division Multiple Access (TDMA), OrthogonalFrequency Division Multiple Access (OFDMA), Single Carrier-FrequencyDivision Multiple Access (SC-FDMA), etc. CDMA may be implemented as aradio technology such as Universal Terrestrial Radio Access (UTRA) orCDMA2000. TDMA may be implemented as a radio technology such as GlobalSystem for Mobile communications (GSM)/General Packet Radio Service(GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may beimplemented as a radio technology such as IEEE 802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE 802.20, Evolved-UTRA (E-UTRA) etc. UTRA is a partof Universal Mobile Telecommunication System (UMTS). 3GPP LTE is a partof Evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA fordownlink and SC-FDMA for uplink. LTE-A is an evolution of 3GPP LTE.WiMAX can be described by the IEEE 802.16e standard (WirelessMetropolitan Area Network (WirelessMAN-OFDMA Reference System) and theIEEE 802.16 m standard (WirelessMAN-OFDMA Advanced System). For clarity,this application focuses on the 3GPP LTE/LTE-A system. However, thetechnical features of the present invention are not limited thereto.

A radio frame structure of 3GPP LTE is described with reference to FIG.1.

In a cellular orthogonal frequency division multiplex (OFDM) wirelesspacket communication system, uplink/downlink data packet transmission isperformed on a subframe basis and a subframe is defined as apredetermined time period including a plurality of OFDM symbols. 3GPPLTE supports a type 1 radio frame structure applicable to frequencydivision duplex (FDD) and a type 2 radio frame structure applicable totime division duplex (TDD).

FIG. 1(a) illustrates the type 1 radio frame structure. A radio frame isdivided into 10 subframes. Each subframe is further divided into twoslots in the time domain. A unit time during which one subframe istransmitted is defined as a transmission time interval (TTI). Forexample, one subframe may be 1 ms in duration and one slot may be 0.5 msin duration. A slot may include a plurality of OFDM symbols in the timedomain and a plurality of resource blocks in the frequency domain.Because 3GPP LTE adopts OFDMA for downlink, an OFDM symbol representsone symbol period. An OFDM symbol may be referred to as an SC-FDMAsymbol or symbol period. A resource block (RB) is a resource allocationunit including a plurality of contiguous subcarriers in a slot.

The number of OFDM symbols included in one slot may be changed accordingto the configuration of a cyclic prefix (CP). The CP includes anextended CP and a normal CP. For example, if the OFDM symbols areconfigured by the normal CP, the number of OFDM symbols included in oneslot may be seven. If the OFDM symbols are configured by the extendedCP, since the length of one OFDM symbol is increased, the number of OFDMsymbols included in one slot is less than that of the case of the normalCP. In case of the extended CP, for example, the number of OFDM symbolsincluded in one slot may be six. If the channel state is unstable, forexample, if a UE moves at a high speed, the extended CP may be used inorder to further reduce interference between symbols.

FIG. 1(b) illustrates the type 2 radio frame structure. The type 2 radioframe includes two half-frames, each of which is made up of fivesubframes, a downlink pilot time slot (DwPTS), a guard period (GP), andan uplink pilot time slot (UpPTS), in which one subframe consists of twoslots. DwPTS is used to perform initial cell search, synchronization, orchannel estimation. UpPTS is used to perform channel estimation of abase station and uplink transmission synchronization of a UE. The guardinterval (GP) is located between an uplink and a downlink so as toremove interference generated in the uplink due to multi-path delay of adownlink signal. One subframe is composed of two slots irrespective ofthe radio frame type.

The radio frame structure is purely exemplary and thus the number ofsubframes in a radio frame, the number of slots in a subframe, or thenumber of symbols in a slot may vary.

FIG. 2 illustrates a resource grid in a downlink slot. A downlink slotincludes 7 OFDM symbols in the time domain and an RB includes 12subcarriers in the frequency domain, which does not limit the scope andspirit of the present invention. For example, a downlink slot includes 7OFDM symbols in case of a normal CP, whereas a downlink slot includes 6OFDM symbols in case of an extended CP. Each element of the resourcegrid is referred to as a resource element (RE). An RB includes 12×7 REs.The number of RBs in a downlink slot, N^(DL) depends on a downlinktransmission bandwidth. An uplink slot may have the same structure as adownlink slot.

Downlink Subframe Structure

FIG. 3 illustrates a downlink subframe structure. Up to three OFDMsymbols at the start of the first slot in a downlink subframe correspondto a control region to which control channels are allocated and theother OFDM symbols of the downlink subframe correspond to a data regionto which a physical downlink shared channel (PDSCH) is allocated.Downlink control channels used in 3GPP LTE include a physical controlformat indicator channel (PCFICH), a physical downlink control channel(PDCCH), and a physical hybrid automatic repeat request (HARQ) indicatorchannel (PHICH). The PCFICH is located in the first OFDM symbol of asubframe, carrying information about the number of OFDM symbols used fortransmission of control channels in the subframe. The PHICH delivers anHARQ acknowledgment/negative acknowledgment (ACK/NACK) signal inresponse to an uplink transmission. Control information carried on thePDCCH is called downlink control information (DCI). The DCI transportsuplink or downlink scheduling information, or uplink transmission powercontrol commands for UE groups. The PDCCH delivers information aboutresource allocation and a transport format for a downlink shared channel(DL-SCH), resource allocation information about an uplink shared channel(UL-SCH), paging information of a paging channel (PCH), systeminformation on the DL-SCH, information about resource allocation for ahigher-layer control message such as a random access responsetransmitted on the PDSCH, a set of transmission power control commandsfor individual UEs of a UE group, transmission power controlinformation, voice over Internet protocol (VoIP) activation information,etc. A plurality of PDCCHs may be transmitted in the control region. AUE may monitor a plurality of PDCCHs. A PDCCH is formed by aggregationof one or more consecutive control channel elements (CCEs). A CCE is alogical allocation unit used to provide a PDCCH at a coding rate basedon the state of a radio channel. A CCE includes a set of REs. The formatof a PDCCH and the number of available bits for the PDCCH are determinedaccording to the correlation between the number of CCEs and a codingrate provided by the CCEs. An eNB determines the PDCCH format accordingto DCI transmitted to a UE and adds a cyclic redundancy check (CRC) tocontrol information. The CRC is masked by an identifier known as a radionetwork temporary identifier (RNTI) according to the owner or usage ofthe PDCCH. If the PDCCH is directed to a specific UE, its CRC may bemasked by a cell-RNTI (C-RNTI) of the UE. If the PDCCH carries a pagingmessage, the CRC of the PDCCH may be masked by a paging indicatoridentifier (P-RNTI). If the PDCCH carries system information,particularly, a system information block (SIB), its CRC may be masked bya system information ID and a System Information RNTI (SI-RNTI). Toindicate that the PDCCH carries a random access response in response toa random access preamble transmitted by a UE, its CRC may be masked by arandom access-RNTI (RA-RNTI).

Downlink Reference Signal

When a packet is transmitted in a wireless communication system, signaldistortion may occur during transmission because the packet istransmitted through a radio channel. To successfully receive a distortedsignal at a receiver, it is necessary to correct distortion of thereceived signal using channel information. To detect the channelinformation, a method of transmitting a signal known to a transmitterand the receiver and detecting the channel information using a degree ofdistortion when the signal is received through the channel is widelyused. The signal is called a pilot signal or a reference signal.

In transmission and reception of data using multiple antennas, thereceiver needs to know channel states between transmit antennas andreceive antennas to successfully receive a signal. Accordingly, aseparate reference signal is needed for each transmit antenna.

Downlink reference signals include a common reference signal (CRS)shared by all UEs in a cell and a dedicated reference signal (DRS) foronly a specific UE. Information for channel estimation and demodulationcan be provided according to these reference signals. The CRS is used toestimate a channel of a physical antenna, can be commonly received byall UEs in a cell, and is distributed in the overall band. The CRS canbe used for acquisition of channel state information (CSI) and datademodulation.

A receiver (UE) can estimate a channel state from the CRS and feed backindicators regarding channel quality, such as a channel qualityindicator (CQI), a precoding matrix index (PMI) and/or a rank indicator(RI), to a transmitter (eNB). The CRS may be called a cell-specificreference signal.

The DRS can be transmitted through a corresponding RE when demodulationof data on a PDSCH is needed. The UE may receive information aboutpresence or absence of a DRS from a higher layer and receive informationrepresenting that the DRS is valid only when a corresponding PDSCH ismapped. The DRS may also be called a UE-specific reference signal ormodulation reference signal (DMRS). The DRS (or UE-specific referencesignal) is used for data demodulation. A precoding weight used for aspecific UE is used for the DRS during multi-antenna transmission suchthat an equivalent channel corresponding a combination of a precodingweight transmitted through each transmit antenna and a transmissionchannel can be estimated when the UE receives the DRS.

FIG. 4 illustrates a pattern of matching a CRS and a DRS defined in 3GPPLTE to a downlink RB pair. A downlink RB pair as a unit to which areference signal is mapped can be represented by a product of onesubframe in the time domain and 12 subcarriers in the frequency domain.That is, one RB pair has a length corresponding to 14 OFDM symbols incase of normal CP and a length corresponding to 12 OFDM symbols in caseof extended CP. FIG. 4 shows an RB pair in case of normal CP.

FIG. 4 shows positions of reference signals on an RB pair in a system inwhich an eNB supports four transmit antennas. In FIG. 4, REs denoted by‘R0’, ‘R1’, ‘R2’ and ‘R3’ correspond to CRS positions for antenna portindexes 0, 1, 2 and 3. REs denoted by ‘D’ correspond to DRS positions.

High-order MIMO (Multiple Input Multiple Output), multi-celltransmission, enhanced multi-user (MU)-MIMO, etc. are considered inLTE-A evolved from 3GPP LTE. To efficiently operate reference signalsand support enhanced transmission schemes, DRS based data demodulationis being considered. That is, a DRS (or UE-specific reference signal orDMRS) for two or more layers can be defined to support data transmissionthrough an additional antenna, separately from a DRS (corresponding toantenna port index 5) for rank 1 beamforming defined in 3GPP LTE (e.g.release-8). For example, UE-specific reference signal ports supportingup to 8 transmit antenna ports can be defined as antenna port numbers 7to 12 and can be transmitted in REs which do not overlap with otherreference signals.

Furthermore, LTE-A may separately define an RS related to feedback ofchannel state information (CSI) such as CQI/PMI/RI for a new antennaport as a CSI-RS. For example, CSI-RS ports supporting up to 8 transmitantenna ports can be defined as antenna port numbers 15 to 22 and can betransmitted in REs which do not overlap with other reference signals.

Uplink Subframe Structure

FIG. 5 illustrates an uplink subframe structure.

Referring to FIG. 5, an uplink subframe may be divided into a controlregion and a data region in the frequency domain. One or more PhysicalUplink Control Channels (PUCCHs) carrying uplink control information maybe allocated to the control region and one or more Physical UplinkShared Channels (PUSCHs) carrying user data may be allocated to the dataregion.

Subcarriers far from a direct current (DC) subcarrier are used for thecontrol region in the UL subframe. In other words, subcarriers at bothends of an uplink transmission bandwidth are allocated for transmissionof uplink control information. The DC subcarrier is a component that isspared from signal transmission and mapped to carrier frequency f₀during frequency upconversion. A PUCCH from one UE is allocated to an RBpair in a subframe and the RBs of the RB pair occupy differentsubcarriers in two slots. This PUCCH allocation is called frequencyhopping of an RB pair allocated to a PUCCH over a slot boundary.However, if frequency hopping is not applied, the RB pair occupies thesame subcarriers.

A PUCCH may be used to transmit the following control information.

-   -   SR (Scheduling Request): used to request UL-SCH resource. This        information is transmitted using OOK (On-Off Keying).    -   HARQ-ACK: response to a PDCCH and/or a response to a downlink        data packet (e.g. codeword) on a PDSCH. This information        represents whether the PDCCH or PDSCH has been successfully        received. 1-bit HARQ-ACK is transmitted in response to a single        downlink codeword and 2-bit HARQ-ACK is transmitted in response        to two downlink codewords. HARQ-ACK responses include positive        ACK (simply, ACK), negative ACK (NACK), DTX (Discontinuous        Transmission) and NACK/DTX. Here, the term HARQ-ACK is used with        HARQ ACK/NACK and ACK/NACK.    -   CSI (Channel State Information): This is feedback information        about a downlink channel. MIMO-related feedback information        includes an RI and a PMI.

The quantity of UCI that can be transmitted by a UE in a subframedepends on the number of SC-FDMA symbols available for controlinformation transmission. SC-FDMA symbols available for UCI correspondto SC-FDMA symbols other than SC-FDMA symbols used for reference signaltransmission in a subframe. In the case of a subframe including asounding reference signal (SRS), the SC-FDMA symbols available for UCIcorrespond to SC-FDMA symbols other than SC-FDMA symbols used forreference signal transmission and the last SC-FDMA symbol in thesubframe. A reference signal is used for PUCCH coherent detection. APUCCH supports various formats according to transmitted information.

PUCCH format 1 is used to transmit SR, PUCCH format 1a/1b is used totransmit ACK/NACK information, and PUCCH format 2 is used to carry CSIsuch as CQI/PMI/RI. PUCCH format 2a/2b is used to carry ACK/NACKinformation with CSI and PUCCH format 3 series is used to transmitACK/NACK information.

UCI Transmission

FIGS. 6 to 10 illustrate UCI transmission using PUCCH format 1 series,PUCCH format 2 series and PUCCH format 3 series.

In 3GPP LTE/LTE-A, a subframe having a normal CP is composed of twoslots each of which includes seven OFDM symbols (or SC-FDMA symbols). Asubframe having an extended CP is composed of two slots each of whichincludes six OFDM symbols (or SC-FDMA symbols). Since the number of OFDMsymbols (or SC-FDMA symbols) per subframe depends on a CP length, aPUCCH transmission structure in a UL subframe is varied according to CPlength. Accordingly, a method of transmitting UCI in a UL subframe by aUE is varied according to PUCCH format and CP length.

Referring to FIGS. 6 and 7, in case of transmission using PUCCH formats1a and 1b, the same control information is repeated on a slot basis in asubframe. UEs transmit ACK/NACK signals through different resourcescomposed of different cyclic shifts (CSs) of a CG-CAZAC(Computer-Generated Constant Amplitude Zero Auto Correlation) sequenceand orthogonal cover codes (OCC). A CS may correspond to a frequencydomain code and an OCC may correspond to a time domain spreading code.An OCC may also be called an orthogonal sequence. An OCC includes aWalsh/DFT (Discrete Fourier Transform) orthogonal code, for example.When the number of CSs is 6 and the number of OCCs is 3, a total of 18PUCCHs can be multiplexed in the same PRB (Physical Resource Block) onthe basis of a single antenna port. An orthogonal sequence w₀, w₁, w₂and w₃ may be applied in a time domain after FFT (Fast FourierTransform) or in a frequency domain before FFT. A PUCCH resource forACK/NACK transmission in 3GPP LTE/LTE-A is represented by a combinationof the position of a time-frequency resource (e.g. PRB), a cyclic shiftof a sequence for frequency spreading and an orthogonal code (orquasi-orthogonal code) for time spreading. Each PUCCH resource isindicated using a PUCCH resource index (PUCCH index). A slot levelstructure of PUCCH format 1 series for SR transmission is identical tothat of PUCCH formats 1a and 1b and a modulation method thereof isdifferent.

FIG. 8 illustrates transmission of CSI in a UL slot having a normal CPusing PUCCH format 2a/2b/2c and FIG. 9 illustrates transmission of CSIin a UL slot having an extended CP using PUCCH format 2a/2b/2c.

Referring to FIGS. 8 and 9, in case of the normal CP, a UL subframe iscomposed of 10 SC-FDMA symbols excepting symbols carrying UL referencesignals (RSs). CSI is coded into 10 transmission symbols (which may becalled complex-valued modulation symbols) through block coding. The 10transmission symbols are respectively mapped to 10 SC-FDMA symbols andtransmitted to an eNB.

PUCCH format 1/1a/1b and PUCCH format 2/2a/2b can carry only UCI havingup to a predetermined number of bits. However, as the quantity of UCIincreases due to introduction of carrier aggregation, a TDD system, arelay system and a multi-node system and an increase in the number ofantennas, a PUCCH format, which is called PUCCH format 3, capable ofcarrying a larger quantity of UCI than PUCCH formats 1/1a/1b/2/2a/2b, isintroduced. For example, PUCCH format 3 can be used for a UE for whichcarrier aggregation is set to transmit a plurality of ACK/NACK signalsfor a plurality of PDSCHs, received from an eNB through a plurality ofdownlink carriers, through a specific uplink carrier.

PUCCH format 3 may be configured on the basis of block spreading, forexample. Referring to FIG. 10, block spreading time-domain-spreads asymbol sequence using an OCC (or orthogonal sequence) and transmits thespread symbol sequence. According to block spreading, control signals ofa plurality of UEs can be multiplexed to the same RB and transmitted toan eNB. In the case of PUCCH format 2, one symbol sequence istransmitted over the time domain, and UCI of UEs is multiplexed using aCS of a CAZAC sequence and transmitted to an eNB. In the case of a newPUCCH format based on block spreading (e.g. PUCCH format 3), one symbolsequence is transmitted over the frequency domain, and UCI of UEs ismultiplexed using OCC based time-domain spreading and transmitted to theeNB. Referring to FIG. 8, one symbol sequence is spread using an OCChaving length-5 (that is, SF=5) and mapped to 5 SC-FDMA symbols. WhileFIG. 10 illustrates a case in which two RS symbols are used in one slot,3 RS symbols may be used and an OCC with SF=4 can be used for symbolsequence spreading and UE multiplexing. Here, the RS symbols can begenerated from a CAZAC sequence having a specific CS. A specific OCC canbe applied to/multiplied by the RS symbols and then the RS symbols canbe transmitted to the eNB. In FIG. 10, DFT may be applied prior to OCC,and FFT (Fast Fourier Transform) may replace DFT.

In FIGS. 6 to 10, a UL RS transmitted with UCI on a PUCCH can be usedfor the eNB to demodulate the UCI.

FIG. 11 illustrates multiplexing of UCI and uplink data in a PUSCHregion.

The uplink data can be transmitted in a data region of a UL subframethrough a PUSCH. A UL DMRS (Demodulation Reference Signal) correspondingto an RS for demodulation of the uplink data can be transmitted with theuplink data in the data region of the UL subframe. The control regionand the data region in the UL subframe are respectively called a PUCCHregion and a PUSCH region.

When UCI needs to be transmitted in a subframe to which PUSCHtransmission is assigned, a UE multiplexes the UCI and uplink data(referred to as PUSCH data hereinafter) prior to DFT-spreading andtransmits the multiplexed UL signal over a PUSCH if simultaneoustransmission of the PUSCH and a PUCCH is not allowed. The UCI includesat least one of CQI/PMI, HARQ ACK/NACK and RI. The number of REs used totransmit each of CQI/PMI, HARQ ACK/NACK and RI is based on a modulationand coding scheme (MCS) and an offset value (Δ_(offset) ^(CQI),Δ_(offset) ^(HARQ-ACK), Δ_(offset) ^(RI)) allocated for PUSCHtransmission. The offset value allows different coding rates accordingto UCI and is semi-statically set through higher layer (e.g. radioresource control (RRC)) signaling. The PUSCH data and UCI are not mappedto the same RE. The UCI is mapped such that it is present in both slotsof the subframe.

Referring to FIG. 11, CQI and/or PMI resource is located at the start ofthe PUSCH data, sequentially mapped to all SC-FDMA symbols in onesubcarrier and then mapped to the next subcarrier. The CQI/PMI is mappedto a subcarrier from the left to the right, that is, in a direction inwhich the SC-FDMA symbols index increases. The PUSCH data israte-matched in consideration of the quantity of a CQI/PMI resource(that is, the number of coded symbols). The same modulation order asthat of UL-SCH data is used for the CQI/PMI. ACK/NACK is inserted intopart of SC-FDMA resource to which the UL-SCH data is mapped throughpuncturing. The ACK/NACK is located beside a PUSCH RS for demodulationof the PUSCH data and sequentially occupies corresponding SC-FDMAsymbols from bottom to top, that is, in a direction in which thesubcarrier index increases. In a normal CP case, SC-FDMA symbols for theACK/NACK correspond to SC-FDMA symbols #2/#5 in each slot, as shown inFIG. 11. Coded RI is located beside a symbol for ACK/NACK irrespectiveof whether the ACK/NACK is actually transmitted in the subframe.

In 3GPP LTE, UCI may be scheduled such that it is transmitted over aPUSCH without PUSCH data. Multiplexing ACK/NACK, RI and CQI/PMI issimilar to that illustrated in FIG. 11. Channel coding and rate matchingfor control signaling without PUSCH data correspond to those for theabove-described control signaling having PUSCH data.

In FIG. 11, the PUSCH RS can be used to demodulate the UCI and/or thePUSCH data transmitted in the PUSCH region. In the present invention, aUL RS related to PUCCH transmission and a PUSCH RS related to PUSCHtransmission are commonly called a DMRS.

A sounding reference signal (SRS) (not shown) may be allocated to thePUSCH region. The SRS is a UL RS that is not related to transmission ofa PUSCH or PUCCH. The SRS is transmitted on the last SC-FDMA symbol of aUL subframe in the time domain and transmitted in a data transmissionband of the UL subframe, that is, a PUSCH region in the frequencydomain. An eNB can measure an uplink channel state between a UE and theeNB using the SRS. SRSs of a plurality of UEs, which aretransmitted/received on the last SC-FDMA symbol of the same subframe,can be discriminated according to frequency positions/sequences thereof.

Uplink Reference Signal

A DMRS transmitted in a PUCCH region and a DMRS and an SRS transmittedin a PUSCH region can be regarded as uplink UE-specific RSs because theyare UE-specifically generated by a specific UE and transmitted to aneNB.

A UL RS is defined by a cyclic shift of a base sequence according to apredetermined rule. For example, an RS sequence r_(u,v) ^((α))(n) isdefined by a cyclic shift α of a base sequence r_(u,v)(n) according tothe following equation.r _(u,v) ^((α))(n)=e ^(jαn) ·r _(u,v)(n),0≦n<M _(sc) ^(RS)  [Equation 1]

Here, M_(sc) ^(RS) is the length of the RS sequence, M_(sc)^(RS)=m·N_(sc) ^(RB) and 1≦m≦N_(RB) ^(max,UL)·N_(RB) ^(max,UL)represented by a multiple of N_(sc) ^(RB) refers to a widest uplinkbandwidth configuration. N_(sc) ^(RB) denotes the size of an RB and isrepresented by the number of subcarriers. A plurality of RS sequencescan be defined from a base sequence through different cyclic shiftvalues α. A plurality of base sequences is defined for a DMRS and anSRS. For example, the base sequences are defined using a root Zadoff-Chusequence. Base sequences r_(u,v)(n) are divided into two groups each ofwhich includes one or more base sequences. For example, each basesequence group can include one base sequence having a length of M_(sc)^(RS)=m·N_(sc) ^(RB) (1≦m≦5) and two base sequences having a length ofM_(sc) ^(RS)=m·N_(sc) ^(RB) (6≦m≦N_(sc) ^(RB)). As to r_(u,v)(n), uε{0,1, . . . ,29} denotes a group number (that is, group index) and vdenotes a base sequence number (that is, base sequence index) in thecorresponding group. Each base sequence group number and a base sequencenumber in the corresponding group may be varied with time.

The sequence group number u in a slot n_(s) is defined by a grouphopping pattern f_(gh)(n_(s)) and a sequence shift pattern f_(ss)according to the following equation.u=(f _(gh)(n _(s))+f _(ss))mod30  [Equation 2]

In Equation 2, mod refers to a modulo operation. A mod B means aremainder obtained by dividing A by B.

A plurality of different hopping patterns (e.g. 30 hopping patterns) anda plurality of different sequence shift patterns (e.g. 17 sequence shiftpatterns) are present. Sequence group hopping may be enabled or disabledaccording to a cell-specific parameter provided by a higher layer.

The group hopping pattern f_(gh)(n_(s)) can be provided by a PUSCH and aPUCCH according to the following equation.

$\begin{matrix}{{f_{gh}\left( n_{s} \right)} = \left\{ \begin{matrix}0 & {{if}\mspace{14mu}{group}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{disabled}} \\{\left( {\sum\limits_{i = 0}^{7}\;{{c\left( {{8\; n_{s}} + i} \right)} \cdot 2^{i}}} \right){mod}\; 30} & {{if}\mspace{14mu}{group}\mspace{14mu}{hopping}\mspace{14mu}{is}\mspace{14mu}{enabled}}\end{matrix} \right.} & \left\lbrack {{Equation}\mspace{14mu} 3} \right\rbrack\end{matrix}$

Here, a pseudo-random sequence c(i) can be defined by a length-31 Goldsequence. An output sequence c(n) (n=0, 1, . . . , M_(PN)−1) having alength of M_(PN) is defined according to the following equation.c(n)=(x ₁(n+N _(C))+x ₂(n+N _(C)))mod2x ₁(n+31)=(x ₁(n+3)+x ₁(n))mod2x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₂(n))mod2  [Equation 4]

Here, N_(C)=1600 and the first m-sequence is initialized to x₁(0)=1,x₁(n)=0, n=1, 2, . . . ,30. Initialization of the second m-sequence isrepresented by the following equation having a value depending onapplication of the sequence.

$\begin{matrix}{c_{init} = {\sum\limits_{i = 0}^{30}\;{{x_{2}(i)} \cdot 2^{i}}}} & \left\lbrack {{Equation}\mspace{14mu} 5} \right\rbrack\end{matrix}$

In Equation 3, a pseudo-random sequence generator is initialized toc_(init) at the start of each radio frame according to the followingequation.

$\begin{matrix}{c_{init} = \left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 6} \right\rbrack\end{matrix}$

In Equation 6, └ ┘ denotes floor operation and └A┘ is a maximum integerless than or equal to A.

According to 3GPP LTE, a PUCCH and a PUSCH have different sequence shiftpatterns although they have the same group hopping pattern according toEquation 3. A sequence shift pattern f_(ss) ^(PUCCH) for the PUCCH isprovided on the basis of cell identification information (cell ID)according to the following equation.f _(ss) ^(PUCCH) =N _(ID) ^(cell) mod30  [Equation 7]

A sequence shift pattern f_(ss) ^(PUSCH) for the PUSCH is givenaccording to the following equation using the sequence shift patternf_(ss) ^(PUCCH) for the PUCCH and a value Δ_(ss) configured by a higherlayer.f _(ss) ^(PUSCH)=(f _(ss) ^(PUCCH)+Δ_(ss))mod30  [Equation 8]

Here, Δ_(ss)ε{0, 1, . . . ,29}.

Base sequence hopping is applied only to RSs having a length of M_(sc)^(RS)≧6N_(sc) ^(RB). For RSs having a length of M_(sc) ^(RS)≧6N_(sc)^(RB), the base sequence number v in a base sequence group is 0. For RSshaving a length of M_(sc) ^(RS)≧6N_(sc) ^(RB), the base sequence numberv in a base sequence group in the slot n_(s) is defined as v=c(n_(s))when group hopping is disabled and sequence hopping is enabled anddefined as v=0 in other cases. Here, the pseudo-random sequence c(i) isgiven by Equation 4. The pseudo-random sequence generator is initializedto c_(init) at the start of each radio frame according to the followingequation.

$\begin{matrix}{c_{init} = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}} & \left\lbrack {{Equation}\mspace{14mu} 9} \right\rbrack\end{matrix}$

A sequence r_(PUCCH) ^((p))(•) of the UL RS (PUCCH DMRS) in FIGS. 6 to10 is given by the following equation.

$\begin{matrix}{{r_{PUCCH}^{(p)}\left( {{m^{\prime}N_{RS}^{PUCCH}M_{sc}^{RS}} + {mM}_{sc}^{RS} + n} \right)} = {\frac{1}{\sqrt{P}}{{\overset{\_}{w}}^{(p)}(m)}{z(m)}{r_{u,v}^{({{\alpha\_}p})}(n)}}} & \left\lbrack {{Equation}\mspace{14mu} 10} \right\rbrack\end{matrix}$

Here, m=0, . . . ,N_(RS) ^(PUCCH)−1, n=0, . . . ,M_(sc) ^(RS)−1, andm′=0, 1. N_(RS) ^(PUCCH) denotes the number of reference symbols perslot for the PUCCH and P denotes the number of antenna ports used forPUCCH transmission. A sequence r_(u,v) ^((α) ^(_) ^(p))(n) is given byEquation 1 having M_(sc) ^(RS)=12, and a cyclic shift α_p is determinedby a PUCCH format.

All PUCCH formats use a cell-specific CS, n_(cs) ^(cell)(n_(s),l) whichhas a value depending on a symbol number l and a slot number n_(s) andis determined as n_(cs) ^(cell)(n_(s),l)=Σ_(i=0) ⁷c(8N_(symb)^(UL)·n_(s)+8l+i)·2^(i). Here, the pseudo-random sequence c(i) isinitialized at the start of each radio frame according toc_(init)=N_(ID) ^(cell).

As to PUCCH formats 2a and 2B, z(m) corresponds to d(10) when m=1, andz(m)=1 in other cases. For PUCCH formats 2a and 2b supported for onlythe normal CP, UCI bits b(20), . . . ,b(M_(bit)−1) from among b(0), . .. , b(M_(bit)−1) are modulated into a single modulation symbol d(10)used to generate a reference signal for PUCCH formats 2a and 2b, asshown in Table 1.

TABLE 1 PUCCH format b(20), . . . , b(M_(bit) − 1) d(10) 2a 0 1 1 −1 2b00 1 01 −j 10 j 11 −1

The PUSCH RS (referred to as PUSCH DMRS hereinafter) in FIG. 11 istransmitted on a layer basis. A PUSCH DMRS sequence r_(PUSCH) ^((p))(·)related to layer λε{0, 1, . . . ,ν−1} is given by the followingequation.r _(PUSCH) ^((λ))(m·M _(sc) ^(RS) +n)=w ^((λ))(m)r _(u,v) ^((α) ^(_)^(λ))(n)  [Equation 11]

Here, m=0, 1, n=0, . . . ,M_(sc) ^(RS)−1, and M_(sc) ^(RS)=M_(sc)^(PUSCH). M_(sc) ^(PUSCH) is a bandwidth scheduled for uplinktransmission and denotes the number of subcarriers. An orthogonalsequence w^((λ))(m) can be given by Table 2 using a cyclic shift fieldin latest uplink-related DCI for transport blocks related to thecorresponding PUSCH. Table 2 illustrates mapping of a cyclic shift fieldin an uplink-related DCI format to n_(DMRS,λ) ⁽²⁾ and [w^((λ))(0)w^((λ))(1)].

TABLE 2 Cyclic Shift Field in uplink-related n_(DMRS, λ) ⁽²⁾ [w^((λ))(0)w^((λ))(1)] DCI format λ = 0 λ = 1 λ = 2 λ = 3 λ = 0 λ = 1 λ = 2 λ = 3000 0 6 3 9 [1 1] [1 1] [1 −1] [1 −1] 001 6 0 9 3 [1 −1] [1 −1] [1 1] [11] 010 3 9 6 0 [1 −1] [1 −1] [1 1] [1 1] 011 4 10 7 1 [1 1] [1 1] [1 1][1 1] 100 2 8 5 11 [1 1] [1 1] [1 1] [1 1] 101 8 2 11 5 [1 −1] [1 −1] [1−1] [1 −1] 110 10 4 1 7 [1 −1] [1 −1] [1 −1] [1 −1] 111 9 3 0 6 [1 1] [11] [1 −1] [1 −1]

A cyclic shift α_λ in the slot n_(s) is given as 2πn_(cs,λ)/12. Here,n_(cs,λ)=(n_(DMRS) ⁽¹⁾+n_(DMRS,λ) ⁽²⁾+n_(PN)(n_(s)))mod12 where n_(DMRS)⁽¹⁾ is given by Table 3 according to a cyclic shift parameter providedthrough higher layer signaling. Table 3 shows mapping of cyclic shiftsto n_(DMRS) ⁽¹⁾ according to higher layer signaling.

TABLE 3 cyclicShift n_(DMRS) ⁽¹⁾ 0 0 1 2 2 3 3 4 4 6 5 8 6 9 7 10

Furthermore, n_(PN)(n_(s)) is given by the following equation using thecell-specific pseudo-random sequence c(i).n _(PN)(n _(s))=Σ_(i=0) ⁷ c(8N _(symb) ^(UL) ·n _(s)+i)·2^(i)  [Equation 12]

Here, the pseudo-random sequence c(i) is defined by Equation 4. Thepseudo-random sequence generator is initialized to c_(init) at the startof each radio frame according to the following equation.

$\begin{matrix}{c_{init} = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}} & \left\lbrack {{Equation}\mspace{14mu} 13} \right\rbrack\end{matrix}$

An SRS sequence r_(SRS) ^((p))(n)=r_(u,v) ^((α) ^(_) ^(p))(n) is definedby Equation 1. Here, u denotes the PUCCH sequence group numberabove-described with respect to group hopping and v denotes the basesequence number above-described with respect to sequence hopping. Thecyclic shift α_p of the SRS is given as follows.

$\begin{matrix}{{{\alpha_{p} = {2\pi\frac{n_{SRS}^{{cs},p}}{8}}}n_{SRS}^{{cs},p} = {\left( {n_{SRS}^{cs} + \frac{8\; p}{N_{ap}}} \right){mod}{\;\;}8}}{p \in \left\{ {0,1,\ldots\mspace{14mu},{N_{ap} - 1}} \right\}}} & \left\lbrack {{Equation}\mspace{14mu} 14} \right\rbrack\end{matrix}$

Here, n_(SRS) ^(cs)={0, 1, 2, 3, 4, 5, 6, 7} is a value configured foreach UE by higher layer parameters and separately generated by differenthigher layer parameters for configurations of periodic sounding andnon-periodic sounding. N_(ap) denotes the number of antenna ports usedfor SRS transmission.

Coordinated Multi-Point: CoMP

CoMP transmission/reception scheme (which is also referred to asco-MIMO, collaborative MIMO or network MIMO) is proposed to meetenhanced system performance requirements of 3GPP LTE-A. CoMP can improvethe performance of a UE located at a cell edge and increase averagesector throughput.

In a multi-cell environment having a frequency reuse factor of 1, theperformance of a UE located at a cell edge and average sector throughputmay decrease due to inter-cell interference (ICI). To reduce ICI, aconventional LTE system uses a method for allowing a UE located at acell edge in an interfered environment to have appropriate throughputusing a simple passive scheme such as fractional frequency reuse (FFR)through UE-specific power control. However, it may be more preferable toreduce ICI or reuse ICI as a signal that a UE desires rather thandecreasing frequency resource use per cell. To achieve this, CoMP can beapplied.

CoMP applicable to downlink can be classified into joint processing (JP)and coordinated scheduling/beamforming (CS/CB).

According to the JP, each point (eNB) of a CoMP coordination unit canuse data. The CoMP coordination unit refers to a set of eNBs used for acoordinated transmission scheme. The JP can be divided into jointtransmission and dynamic cell selection.

The joint transmission refers to a scheme through which PDSCHs aresimultaneously transmitted from a plurality of points (some or all CoMPcoordination units). That is, data can be transmitted to a single UEfrom a plurality of transmission points. According to jointtransmission, quality of a received signal can be improved coherently ornon-coherently and interference on other UEs can be actively erased.

Dynamic cell selection refers to a scheme by which a PDSCH istransmitted from one point (in a CoMP coordination unit). That is, datais transmitted to a single UE from a single point at a specific time,other points in the coordination unit do not transmit data to the UE atthe time, and the point that transmits the data to the UE can bedynamically selected.

According to the CS/CB scheme, CoMP coordination units cancollaboratively perform beamforming of data transmission to a single UE.Here, user scheduling/beaming can be determined according tocoordination of cells in a corresponding CoMP coordination unit althoughdata is transmitted only from a serving cell.

In case of uplink, coordinated multi-point reception refers to receptionof a signal transmitted according to coordination of a plurality ofpoints geographically spaced apart from one another. A CoMP receptionscheme applicable to uplink can be classified into joint reception (JR)and coordinated scheduling/beamforming (CS/CB).

JR is a scheme by which a plurality of reception points receives asignal transmitted over a PUSCH and CS/CB is a scheme by which userscheduling/beamforming is determined according to coordination of cellsin a corresponding CoMP coordination unit while one point receives aPUSCH.

A UE can receive data from multi-cell base stations collaborativelyusing the CoMP system. The base stations can simultaneously support oneor more UEs using the same radio frequency resource, improving systemperformance. Furthermore, a base station may perform space divisionmultiple access (SDMA) on the basis of CSI between the base station anda UE.

In the CoMP system, a serving eNB and one or more collaborative eNBs areconnected to a scheduler through a backbone network. The scheduler canoperate by receiving channel information about a channel state betweeneach UE and each collaborative eNB, measured by each eNB, through thebackbone network. For example, the scheduler can schedule informationfor collaborative MIMO operation for the serving eNB and one or morecollaborative eNBs. That is, the scheduler can directly directcollaborative MIMO operation to each eNB.

As described above, the CoMP system can be regarded as a virtual MIMOsystem using a group of a plurality of cells. Basically, a communicationscheme of MIMO using multiple antennas can be applied to CoMP.

Enhanced Uplink Signal Transmission Scheme

Referring to Equations 1 to 14, UEs located in a cell initialize thepseudo-random sequence generator that generates RS sequences using thesame N_(ID) ^(cell). Because a UE transmits an uplink signal only to onecell, the UE uses only one N_(ID) ^(cell) in order to generate a PUSCHDMRS, PUCCH DMRS and SRS. That is, in a conventional system in which aUE transmits an uplink signal only to one cell, a UE based DMRS sequenceis used. In other words, since the conventional communication systemperforms uplink transmission only for one cell, a UE can acquire N_(ID)^(cell) (i.e. physical layer cell ID) on the basis of a downlink PSS(Primary Synchronization Signal) received from the serving cell and usethe acquired N_(ID) ^(cell) to generate an uplink RS sequence.

However, in uplink CoMP, a UE can transmit an uplink signal to aplurality of cells or reception points (RPs) or to some of the cells orRPs. In this case, when an uplink transmitting side transmits an RSsequence generated according to a conventional method, a receiving sidemay not detect the RS.

Accordingly, for CoMP in which a plurality of cells or RPs participatesin communication with a UE, it is necessary to define DMRS generation,resource allocation and/or transmission schemes for data transmitted todifferent points even if the different points do not simultaneouslyreceive the data. While one RP can receive an uplink signal from a UEthrough one or more cells, a cell receiving an uplink signal is calledan RP in the following description for convenience.

The present invention proposes a method by which a CoMP UE generates aDMRS sequence used for PUSCH transmission and/or PUCCH transmission in amulti-cell (multi-RP) environment.

FIG. 1 is a diagram for explaining an exemplary UL CoMP operation.

In an uplink CoMP operation by which one UE (i.e. CoMP UE) transmits aPUSCH to a plurality of cells (or RPs), it is important to ensure mutualorthogonality between uplink DMRSs. If mutual orthogonality betweenuplink DMRSs is not ensured, each RP cannot correctly estimate an uplinkchannel, and thus PUSCH demodulation performance is considerablydeteriorated. The UE can generate a DMRS base sequence using the cell IDof a serving cell and apply an OCC for orthogonality with other DMRSs asnecessary. Specifically, the uplink DMRS base sequence is a function ofthe cell ID, and a PUSCH DMRS base sequence index having an offset ofΔ_(ss) from a PUCCH DMRS base sequence index is determined Here, Δ_(ss)is given through higher layer signaling (e.g. RRC signaling). That is,the same cell ID is applied to generation of base sequences of PUCCHDMRS and PUSCH DMRS and a base sequence index offset of Δ_(ss) isprovided between the base sequences of PUCCH DMRS and PUSCH DMRS (referto Equation 8). For example, if Δ_(ss)=0 is signaled through RRCsignaling, the PUCCH DMRS and PUSCH DMRS may have the same basesequence.

In case of the CoMP UE, a DL serving cell and a UL serving cell may bedifferent from each other, and thus the cell ID of the DL serving cellcannot be used to generate a UL DMRS base sequence and the UL DMRS basesequence needs to be generated using the cell ID of an RP according todetermination by a scheduler. That is, the UL DMRS base sequence needsto be generated using the ID of a cell other than the serving cell. Toprovide scheduling flexibility in determination of UEs paired forMU-MIMO, it is desirable to dynamically indicate a cell ID used togenerate a UL DMRS. For example, a higher layer can signal setting of aplurality of DMRSs (including setting of a DMRS for cell A and settingof a DMRS for cell B) to a CoMP UE located at edges of a cell A and acell B shown in FIG. 12. The CoMP UE may be co-scheduled with another UE(UE-A) of the cell A or another UE (UE-B) of the cell B according tochannel condition and/or other network conditions. That is, a DMRS basesequence of the CoMP UE can be generated using the ID of a cell to whicha UE co-scheduled with the CoMP UE belongs. The cell ID used for DMRSbase sequence generation can be dynamically selected or indicated.

To support the above-described uplink CoMP operation, the presentinvention can provide a cell ID to be used to generate a PUSCH DMRSsequence to a UE through UE-specific higher layer signaling (e.g. RRCsignaling). The cell ID used to generate the PUSCH DMRS sequence can beindicated using a parameter such as N_(ID) ^((PUSCH)) or n_(ID)^((PUSCH)) to be discriminated from a cell ID (that is, a parameterN_(ID) ^(cell) representing a physical layer cell ID (PCI)) used togenerate a conventional DMRS sequence. Here, N_(ID) ^((PUSCH)) or n_(ID)^((PUSCH)) may be called a virtual cell ID (VCI) for PUSCH DMRS sequencegeneration. The virtual cell ID (referred to as “PUSCH DMRS VCI”) forPUSCH DMRS sequence generation may have a value identical to ordifferent from the PCI.

According to the conventional operation, a sequence shift pattern f_(ss)^(PUSCH) for the PUSCH DMRS is determined using a sequence shift patternf_(ss) ^(PUCCH) for the PUCCH and the sequence shift related offsetΔ_(ss) set by a higher layer (refer to Equations 7 and 8). When f_(ss)^(PUCCH) of Equation 7 is applied to Equation 8, the following equation15 is obtained.f _(ss) ^(PUSCH)=((N _(ID) ^(cell) mod30)+Δ_(ss))mod30=(N _(ID)^(cell)+Δ_(ss))mod 30  [Equation 15]

When use of the PUSCH DMRS VCI parameter (e.g. N_(ID) ^((PUSCH)) orn_(ID) ^((PUSCH))) is set by a higher layer, the offset Δ_(ss) set bythe higher layer may be used in the present invention. This may becalled a first scheme for setting Δ_(ss).

Furthermore, when use of the PUSCH DMRS VCI parameter (e.g. N_(ID)^((PUSCH)) or n_(ID) ^((PUSCH))) is set by the higher layer, the presentinvention may generate a PUSCH DMRS sequence using a predetermined (orpre-appointed) specific offset value Δ_(ss) instead of the offset Δ_(ss)set by the higher layer. That is, when the higher layer signals thePUSCH DMRS VCI parameter (e.g. N_(ID) ^((PUSCH)) or n_(ID) ^((PUSCH)))to a UE, the UE can be configured to use the predetermined offset Δ_(ss)instead of the offset Δ_(ss) previously used by the UE (or set by thehigher layer). This may be called a second scheme for setting Δ_(ss).

As an example of the second scheme for setting Δ_(ss), the presentinvention may previously determine a rule such that operation isperformed on the basis of Δ_(ss)=0 when the higher layer sets use of thePUSCH DMRS VCI parameter N_(ID) ^((PUSCH)) or n_(ID) ^((PUSCH)). Thismay be called a third scheme for setting Δ_(ss).

For example, the PUSCH DMRS VCI parameter N_(ID) ^((PUSCH)) or n_(ID)^((PUSCH)) can replace the physical cell ID parameter N_(ID) ^(cell) andΔ_(ss) can be set to 0 in Equation 15. This is arranged as follows.f _(ss) ^(PUSCH) =N _(ID) ^((PUSCH))mod30orf _(ss) ^(PUSCH) =n _(ID) ^((PUSCH))mod30  [Equation 16]

A plurality of PUSCH DMRS VCI values N_(ID) ^((PUSCH)) or n_(ID)^((PUSCH)) may be set by the higher layer and a value to be used fromamong the plurality of PUSCH DMRS VCI values N_(ID) ^((PUSCH)) or n_(ID)^((PUSCH)) may be dynamically indicated through uplink scheduling grantinformation (that is, uplink-related DCI). Here, when the PUSCH DMRS VCIvalues N_(ID) ^((PUSCH)) or n_(ID) ^((PUSCH)) are set by the higherlayer, specific values Δ_(ss) respectively mapped to the PUSCH DMRS VCIvalues may be used.

To dynamically indicate one of the PUSCH DMRS VCI values N_(ID)^((PUSCH)) or n_(ID) ^((PUSCH)) through the uplink-related DCI, a bit(or bits) for indicating a virtual cell ID may be newly added to theuplink-related DCI format to explicitly indicate the corresponding VCIor an existing bit (or bits) may be reused. For example, a mappingrelationship can be established such that one of states of a 3-bit“Carrier Indicator” field or a 3-bit “Cyclic Shift for DMRS and OCCindex” field from among bit fields of the uplink-related DCI (e.g. DCIformat 0 or 4) implicitly indicates one of the PUSCH DMRS VCI valuesN_(ID) ^((PUSCH)) or n_(ID) ^((PUSCH)).

A case in which the PUSCH DMRS VCI N_(ID) ^((PUSCH)) or n_(ID)^((PUSCH)) is set by the higher layer has been described in the aboveembodiment. The present invention proposes a scheme forsetting/providing a virtual cell ID (referred to as “PUCCH DMRS VCI”)used to generate a PUCCH DMRS sequence through UE-specific higher layersignaling (e.g. RRC signaling). A PUCCH DMRS VCI parameter may beindicated by N_(ID) ^((PUSCH)) or n_(ID) ^((PUSCH)).

While the same cell ID (i.e. physical cell ID parameter N_(ID) ^(cell))is used to generate a PUSCH DMRS sequence and a PUCCH DMRS sequence inconventional operations, the present invention proposes a scheme ofseparately (independently) setting the PUSCH DMRS VCI (that is, N_(ID)^((PUSCH)) or n_(ID) ^((PUSCH))) and the PUCCH DMRS VCI (that is, N_(ID)^((PUCCH)) or n_(ID) ^((PUCCH))).

For simplicity, the PUSCH DMRS VCI and the PUCCH DMRS VCI may berepresented as one parameter n_(ID) ^(RS). In this case, n_(ID) ^(RS)can be determined according to transmission type. That is, n_(ID) ^(RS)can be defined as n_(ID) ^((PUSCH)) in case of PUSCH relatedtransmission and n_(ID) ^(RS) can be defined as n_(ID) ^((PUCCH)) incase of PUCCH related transmission. Here, while one parameter n_(ID)^(RS) is used, n_(ID) ^((PUSCH)) (or N_(ID) ^((PUSCH))) and n_(ID)^((PUCCH)) (or n_(ID) ^((PUCCH))) are defined as separate parameters.That is, it should be understood that n_(ID) ^((PUSCH)) (or N_(ID)^((PUSCH))) and n_(ID) ^((PUCCH)) (or n_(ID) ^((PUCCH))) can be set by ahigher layer as separate parameters.

A case in which a PUCCH related VCI (that is, n_(ID) ^((PUCCH)) orN_(ID) ^((PUCCH))) and a PUSCH related VCI (that is, n_(ID) ^((PUSCH))or N_(ID) ^((PUSCH))) are different from each other may represent that aUE respectively transmits a PUCCH and a PUSCH to different RPs. That is,the PUCCH may be transmitted to an RP (or RPs) corresponding to n_(ID)^((PUCCH)) or N_(ID) ^((PUCCH)) and the PUSCH may be transmitted to anRP (or RPs) corresponding to n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH)).

A plurality of PUCCH DMRS VCI values N_(ID) ^((PUCCH)) or n_(ID)^((PUCCH)) may be set by the higher layer and a value to be used fromamong the plurality of PUCCH DMRS VCI values N_(ID) ^((PUCCH)) or n_(ID)^((PUCCH)) may be dynamically indicated through uplink-related DCI. Todynamically indicate one of the PUCCH DMRS VCI values, a method ofimplicitly indicating a PUCCH DMRS VCI through a state of a specific bitfield of an uplink-related DCI format or a method of adding a new bitfield (or bit fields) to explicitly indicate a PUCCH DMRS DCI may beused. For example, a mapping relationship can be established such thatone of states of “HARQ process number” field (which is defined as 3 bitsin case of FDD and 4 bits in case of TDD) of an uplink-related DCIformat (e.g. DCI format 0 or 4) implicitly indicates one of the PUCCHDMRS VCI values. Otherwise, a mapping relationship can be establishedsuch that one of states of a bit field (e.g. downlink DMRS sequencegeneration can be performed using a scrambling ID value indicated by3-bit “Antenna port(s), scrambling identity and number of layers”field), which indicates a downlink DMRS (or UE-specific RS) parameter inDCI (e.g. DCI format 2C) for downlink allocation, implicitly indicatesone of the PUCCH DMRS VCI values.

The above-described embodiment of the present invention is representedby equations as follows.

When the pseudo-random sequence c(i) used to determine the group hoppingpattern f_(gh)(n_(s)) of an uplink DMRS is generated according toEquations 3 and 6, the present invention can initialize thepseudo-random sequence generator to c_(init) at the start of each radioframe according to the following equation. That is, Equation 6 can bereplaced by Equation 17.

$\begin{matrix}{c_{init} = \left\lfloor \frac{n_{ID}^{RS}}{30} \right\rfloor} & \left\lbrack {{Equation}\mspace{14mu} 17} \right\rbrack\end{matrix}$where n_(ID) ^(RS)=n_(ID) ^((PUSCH)) or n_(ID) ^(RS)=N_(ID) ^((PUSCH))for a PUSCH, and n_(ID) ^(RS)=n_(ID) ^((PUCCH)) or n_(ID) ^(RS)=N_(ID)^((PUCCH)) for a PUCCH.

Equation 17 may be represented as Equation 18.

$\begin{matrix}{{c_{init} = {{\left\lfloor \frac{N_{ID}^{({PUSCH})}}{30} \right\rfloor\mspace{14mu}{or}\mspace{14mu} c_{init}} = \left\lfloor \frac{n_{ID}^{({PUSCH})}}{30} \right\rfloor}}{{{for}\mspace{14mu}{PUSCH}},{and}}{c_{init} = {{\left\lfloor \frac{N_{ID}^{({PUCCH})}}{30} \right\rfloor\mspace{14mu}{or}\mspace{14mu} c_{init}} = \left\lfloor \frac{n_{ID}^{({PUCCH})}}{30} \right\rfloor}}{{for}\mspace{14mu}{PUCCH}}} & \left\lbrack {{Equation}\mspace{14mu} 18} \right\rbrack\end{matrix}$

The sequence shift parameter f_(ss) ^(PUCCH) for PUCCH DMRS can berepresented by the following equation.f _(ss) ^(PUCCH) =n _(ID) ^(RS) mod30  [Equation 19]where n_(ID) ^(RS)=n_(ID) ^((PUCCH)) or n_(ID) ^(RS)=N_(ID) ^((PUCCH))for a PUCCH.

Equation 18 may be represented as Equation 20.f _(SS) ^(PUCCH) =N _(ID) ^((PUCCH))mod30 or f _(SS) ^(PUCCH) =n _(ID)^((PUCCH))mod30  [Equation 20]

When the sequence shift parameter f_(ss) ^(PUSCH) for PUSCH DMRS isdetermined, f_(ss) ^(PUSCH) can be represented by Equation 21 whenΔ_(ss) is predefined as 0 as represented by Equation 16.f _(ss) ^(PUSCH) =n _(ID) ^(RS) mod30  [Equation 21]where n_(ID) ^(RS)=n_(ID) ^((PUSCH)) or n_(ID) ^((PUSCH)) for a PUSCH.

Equation 21 may be represented as Equation 16 (that is, f_(ss)^(PUSCH)=N_(ID) ^((PUSCH))mod 30 or f_(ss) ^(PUSCH)=n_(ID) ^((PUSCH))mod30).

Here, it should be noted that n_(ID) ^((PUSCH)) (or N_(ID) ^((PUSCH)))and n_(ID) ^((PUSCH)) (or n_(ID) ^((PUSCH))), which are different fromeach other, are actually applied as VCI values (i.e. n_(ID) ^(RS))although f_(ss) ^(PUCCH) and f_(ss) ^(PUSCH) are defined in the sameequation form in Equations 19 and 21.

When the scheme (the third scheme for setting Δ_(ss)) represented byEquation 21 is applied, even if a value Δ_(ss) set through higher layersignaling has been provided to a corresponding UE, f_(ss) ^(PUSCH) iscalculated by setting Δ_(ss) to 0 when the PUSCH VCI (i.e. n_(ID)^((PUSCH)) or n_(ID) ^((PUSCH))) is set by higher layer signaling.

Alternatively, in determination of the sequence shift parameter f_(ss)^(PUSCH) for PUSCH DMRS, f_(ss) ^(PUSCH) can be represented by Equation22 when the value Δ_(ss) set by the higher layer is used (that is, thefirst scheme for setting Δ_(ss)) or a predetermined specific valueΔ_(ss) is used (that is, the second scheme for setting Δ_(ss)).f _(ss) ^(PUSCH)={(n _(ID) ^(RS) mod30)+Δ_(ss)} mod30  [Equation 22]where n_(ID) ^(RS)=n_(ID) ^((PUSCH)) or n_(ID) ^(RS)=N_(ID) ^((PUSCH))for a PUSCH.

In Equation 22, Δ_(ss)ε{0, 1, . . . , 29}.

Equation 22 may be represented as the following equation.f _(ss) ^(PUSCH)={(N _(ID) ^((PUSCH))mod30)+Δ_(ss)} mod 30orf _(ss) ^(PUSCH)={(n _(ID) ^((PUSCH))mod30)+Δ_(ss)} mod30  [Equation 23]

According to the first scheme for setting Δ_(ss), f_(ss) ^(PUSCH) can becalculated using the value Δ_(ss) set by higher layer signaling andpreviously provided to the corresponding UE and the PUSCH VCI (that is,n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) signaled by the higher layer.

According to the second scheme for setting Δ_(ss), even if the valueΔ_(ss) set by higher layer signaling has been provided to thecorresponding UE,f_(ss) ^(PUSCH) can be calculated by setting Δ_(ss) toa specific value s (sε{0, 1, . . . ,29}) when the PUSCH VCI (that is,n_(ID) ^((PUSCH)) or N_(ID) ^(PUSCH))) is set through higher layersignaling.

According to the above-described embodiments, a group hopping patternf_(gh)(n_(s)) of a UE for which a value A is set by a higher layer as aPUSCH DMRS VCI (that is, n_(ID) ^((PUSCH)) or N_(ID) ^(PUSCH)))corresponds to group hopping patterns of other UEs (that is, UEs forwhich a PCI is set to A and/or UEs for which a PUSCH VCI is set to A)using the value A as a cell ID. Furthermore, when the same Δ_(ss)(particularly, Δ_(ss)=0) is applied to determination of the sequenceshift pattern f_(ss) ^(PUSCH), the sequence shift pattern of the UE forwhich the PUSCH VCI is set corresponds to PUSCH DMRS sequence shiftpatterns of the other UEs. Accordingly, base sequence indexes u of UEswhich use the same group hopping pattern and the same sequence shiftpattern are identical (refer to Equation 2). This means thatorthogonality can be given between DMRSs of the UEs by respectivelyapplying different CSs to the UEs. That is, the present invention canprovide orthogonality between PUSCH DMRSs of UEs belonging to differentcells by setting a PUSCH DMRS VCI for a specific UE, distinguished froma conventional wireless communication system in which orthogonalitybetween PUSCH DMRSs is given using different CSs in the same cell.Accordingly, MU-MIMO pairing for UEs belonging to different cells can beachieved and enhanced UL CoMP operation can be supported.

Furthermore, even when different PUSCH DMRS VCI values are set for aplurality of UEs, orthogonality between PUSCH DMRSs can be provided bymaking the plurality or UEs use the same PUSCH DMRS base sequence.

Specifically, the first, second and third schemes for setting Δ_(ss)correspond to a rule of determining a value Δ_(ss) to be used when thePUSCH DMRS VCI (that is, n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) issignaled by a higher layer. On the assumption that one of the schemes isapplied, an eNB can select an appropriate PUSCH DMRS VCI (that is,n_(ID) ^((PUSCH)) or N_(ID) ^(PUSCH))) in consideration of a valueΔ_(ss) to be used and signal the selected PUSCH DMRS VCI to a UE. Here,c_(init), which is a factor (or a seed value) for determining the grouphopping pattern f_(gh)(n_(s)), is determined as the same value for 30different VCI values (that is, n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))according to a floor operation as represented by Equations 17 and 18.Accordingly, it is possible to set f_(ss) ^(PUSCH) to a specific valueby selecting an appropriate one of the 30 different VCI valuesgenerating the same group hopping pattern f_(gh)(n_(s)). That is, grouphopping patterns f_(gh)(n_(s)) respectively calculated by two differentUEs can be identical to each other even though different VCIs are setfor the two UEs. Furthermore, sequence shift patterns f_(ss) ^(PUSCH)respectively calculated by the two UEs can be identical to each other.An appropriate VCI (that is, n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH)))that makes group hopping patterns f_(gh)(n_(s)) and sequence shiftpatterns f_(ss) ^(PUSCH) of MU-MIMO-paired UEs correspond to each othercan be set through a higher layer. Accordingly, PUSCH DMRS basesequences of the UEs become identical, and thus orthogonality betweenPUSCH DMRSs can be provided according to a method of applying differentCSs to the UEs.

In addition, a plurality of UEs can have the same group hopping patternf_(gh)(n_(s)) and the same sequence shift pattern f_(ss) ^(PUSCH)through a method of setting a UE-specific VCI (that is, n_(ID)^((PUSCH)) or N_(ID) ^((PUSCH))) and/or a method of setting aUE-specific Δ_(ss). Here, since a method of additionallyhigher-layer-signaling a value Δ_(ss) to each UE may generateunnecessary overhead, it is possible to make the UEs have the same grouphopping pattern f_(gh)(n_(s)) and the same sequence shift pattern f_(ss)^(PUSCH) by signaling only the UE-specific VCI without separatelysignaling Δ_(ss).

Alternatively, the PUSCH transmission related VCI (that is, n_(ID)^((PUSCH)) or N_(ID) ^((PUSCH))) may be used only when f_(ss) ^(PUSCH)is determined. That is, the PCI (that is, N_(ID) ^(cell)) of the currentserving cell is used for f_(ss) ^(PUSCH), as represented by Equation 7,and the VCI (that is, n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) proposedby the present invention is used for f_(ss) ^(PUSCH) to separate a PUCCHsequence and a PUSCH sequence from each other.

Alternatively, N_(ID) ^((PUSCH)) may also be applied to f_(ss) ^(PUCCH).That is, f_(ss) ^(PUCCH) can be defined by Equation 24.f _(SS) ^(PUCCH) =N _(ID) ^((PUSCH))mod30 or f _(ss) ^(PUCCH) =n _(ID)^((PUSCH))mod 30  [Equation 24]

Equation 24 represents that a UE-specific VCI (N_(ID)) is set by higherlayer signaling and commonly used to determine f_(ss) ^(PUCCH) andf_(ss) ^(PUSCH). That is, a PUCCH and a PUSCH are transmitted from acorresponding UE to an RP (or RPs) using a UE-specific N_(ID) by settingthe UE-specific N_(ID).

The scope of the present invention is not limited to the above-describedembodiments and can include various methods for allowing UEs to have thesame PUSCH DMRS sequence group hopping pattern f_(gh)(n_(s)) and/or thesame shift pattern f_(ss) ^(PUSCH) by setting a UE-specific VCI.

When group hopping is disabled and sequence hopping is enabled, sequencehopping according to a conventional method can be defined as representedby Equation 9. As proposed by the present invention, when a UE-specificVCI (that is, n_(ID) ^(PUSCH)) or N_(ID) ^((PUSCH))) is set by a higherlayer and sequence hopping is enabled, the pseudo-random sequencegenerator can be initialized to c_(init) at the start of each radioframe according to the following equation.

$\begin{matrix}{c_{init} = {{\left\lfloor \frac{n_{ID}^{RS}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}} & \left\lbrack {{Equation}\mspace{14mu} 25} \right\rbrack\end{matrix}$where n_(ID) ^(RS)=n_(ID) ^((PUSCH)) or n_(ID) ^(RS)=N_(ID) ^((PUSCH))for a PUSCH.

The VCI (that is, n_(ID) ^(RS) (n_(ID) ^(RS)=n_(ID) ^((PUSCH)) or n_(ID)^(RS)=N_(ID) ^((PUSCH)) for PUSCH transmission)) used in Equation 25 maycorrespond to the PUSCH DMRS VCI signaled to the UE through higher layersignaling, which is described in the other embodiments. In addition,f_(ss) ^(PUSCH) in Equation 25 may correspond to the value determinedaccording to Equation 16, 21, 22 or 23 (that is, a value determinedaccording to the first, second or third scheme for setting Δ_(ss)).

Specifically, n_(ID) ^(RS) and f_(ss) ^(PUSCH) in Equation 25 can usethe same values as n_(ID) ^(RS) and f_(ss) ^(PUSCH) determined to makegroup hopping patterns f_(gh)(n_(s)) and sequence hopping patternsf_(ss) ^(PUSCH) set for MU-MIMO-paired UE equal to each other when thethird scheme (that is, a scheme of determining Δ_(ss) as 0 withoutadditional higher layer signaling for setting Δ_(ss)) for setting Δ_(ss)is applied.

Scheme of Setting Range of Virtual Cell ID Value

As described above, the first VCI (e.g. n_(ID) ^((PUCCH)) or N_(ID)^((PUCCH)) for the PUCCH DMRS and the second VCI (e.g. n_(ID) ^((PUSCH))or N_(ID) ^((PUSCH)) for the PUSCH DMRS can be provided as separateparameters.

Here, the first VCI (e.g. n_(ID) ^((PUCCH)) or N_(ID) ^((PUCCH))) forthe PUCCH DMRS can be set to one of 504 values (i.e. 0 to 503) like thePCI. In the conventional wireless communication system, the sequenceshift pattern f_(ss) ^(PUCCH) for a PUCCH is calculated without usingΔ_(ss) according to Equation 7, f_(ss) ^(PUCCH)=N_(ID) ^(cell) mod 30.When the first VCI (e.g. n_(ID) ^((PUCCH)) or N_(ID) ^((PUCCH))) for aPUCCH is set through higher layer signaling according to the presentinvention, f_(ss) ^(PUCCH) is calculated without using Δ_(ss) accordingto Equation 20, f_(ss) ^(PUCCH)=N_(ID) ^((PUCCH))mod 30 or f_(ss)^(PUCCH)=n_(ID) ^((PUCCH))mod 30. Accordingly, sequence shift operationcan be successfully supported even when the range of the first VCI for aPUCCH is limited to 0 to 503 as the PCI.

When the second VCI (e.g. n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) for aPUSCH has the same range as that of the PCI, sequence shift for thePUSCH DMRS cannot be successfully supported. In the conventionalwireless communication system, the sequence shift pattern f_(ss)^(PUSCH) for a PUSCH is calculated without using Δ_(ss) according toEquation 8, f_(ss) ^(PUSCH)=(f_(ss) ^(PUCCH)+Δ_(ss))mod 30. According tothe scheme (particularly, the third scheme for setting Δ_(ss)) proposedby the present invention, however, when the second VCI (e.g. n_(ID)^((PUSCH)) or N_(ID) ^((PUSCH))) for a PUSCH is set, f_(ss) ^(PUSCH) iscalculated without using Δ_(ss) according to Equation 16, f_(ss)^(PUSCH)=N_(ID) ^((PUSCH))mod 30 or f_(ss) ^(PUSCH)=n_(ID) ^((PUSCH))mod30. The scheme of using the PCI and Δ_(ss) in the conventional wirelesscommunication system was employed in order to cover 30 base sequencegroups and 17 sequence group hopping patterns. That is, the offset valueΔ_(ss) was additionally used because all 510 (that is, 30 base sequencegroups×17 sequence group hopping patterns) cases cannot be covered whenbased on only the PCI since the range of the PCI is limited to 0 to 503.Accordingly, to determine f_(ss) ^(PUSCH) using only the second VCI fora PUSCH without using Δ_(ss), it is necessary to correct the range ofthe second VCI (e.g. n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))).

Therefore, the present invention defines the range of the value of thesecond VCI (e.g. n_(ID) ^((PUSCH)) or N_(ID) ^((PUSCH))) as 0 to 509. Inthis case, it is possible to cover all the 510 (30×17) cases accordingto different base sequence groups and different sequence group hoppingpatterns.

Definition/setting/provision of the first VCI (e.g. n_(ID) ^((PUCCH)) orN_(ID) ^((PUCCH))) for the PUCCH DMRS and the second VCI (e.g. n_(ID)^((PUSCH)) or N_(ID) ^((PUSCH))) for the PUSCH DMRS as separateparameters may mean that the available range (i.e. 0 to 503) of thefirst VCI and the available range (i.e. 0 to 509) of the second VCI aredifferent from each other.

In addition, the VCI range may be set such that it includes at least 0to 509 in order to cover 510 (=30×17) different pattern using a singleVCI.

For example, the VCI range can be set to 0 to 511 considering that atleast 9 bits are necessary to represent 509 states because 9 bits canindicate a maximum of 512 states.

Furthermore, the VCI range can be increased to 0 to 1023, which supportsa bit width of 10 bits capable of representing 1024 states. If one ormore of group hopping, sequence shift, sequence hopping and CS hoppingrequire a new pattern, an increased VCI range can be defined and used.

UE Operation Relating to Uplink Reference Signal Generation

A scheme (referred to as a scheme A hereinafter) for supporting backwardcompatibility) in consideration of operation of a UE (referred to aslegacy-UE hereinafter) according to the legacy wireless communicationsystem and a scheme (referred to as a scheme B hereinafter) optimizedfor operation of a UE (advanced-UE (A-UE)) according to an advancedwireless communication system will be described in detail on the basisof the above-described uplink reference signal generation schemeaccording to the present invention.

The scheme A can be considered to be related to the first scheme (i.e.scheme of using Δ_(ss) set by a higher layer without change) for settingΔ_(ss) and the scheme B can be considered to be related to the second orthird scheme (i.e. scheme of ignoring Δ_(ss) set by a higher layer andusing a specific value of Δ_(ss) (particularly, Δ_(ss)=0) for settingΔ_(ss). However, the schemes A and B are not limited to the first,second and third schemes for setting Δ_(ss).

Scheme A

An uplink reference signal generation operation capable of supportingbackward compatibility with the legacy wireless communication system andUE operation will now be described. A UE can acquire the cell-specificparameter Δ_(ss) for UL RS sequence generation during initial cellaccess such as a random access procedure through higher layer signaling.In addition, the UE can acquire the PCI (that is, N_(ID) ^(cell)) of thecorresponding cell on the basis of PSS and SSS.

The UE can calculate f_(ss) ^(PUSCH) for PUSCH transmission using theacquired PCI and Δ_(ss) (refer to Equation 8), and thus the UE cancalculate a cyclic shift hopping (CSH) pattern of a PUSCH DMRS (refer toEquations 12 and 13). Here, an initial value c_(init) ^(CSH) of apseudo-random sequence c(i) that determines the CSH pattern can berepresented by Equation 26 when f_(ss) ^(PUSCH) in Equation 13 isreplaced by f_(ss) ^(PUSCH) in equation 8 and f_(ss) ^(PUCCH) inEquation 6 is replaced by f_(ss) ^(PUCCH) in equation 7.

$\begin{matrix}\begin{matrix}\left. {c_{init}^{CSH} = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + {\left( {\left( {N_{ID}^{cell}{mod}\mspace{14mu} 30} \right) + \Delta_{ss}} \right){mod}\mspace{14mu} 30}}} \right) \\{= {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + \left( {\left( {N_{ID}^{cell} + \Delta_{ss}} \right){mod}\mspace{14mu} 30} \right)}}\end{matrix} & \left\lbrack {{Equation}\mspace{14mu} 26} \right\rbrack\end{matrix}$

That is, the UE can acquire a parameter set {PCI, Δ_(ss), c_(init)^(CSH)} in the initial access procedure and thus can generate a UL RSsequence.

Scheme A-1

PUCCH DMRS, PUSCH DMRS and SRS sequences can be generated by applyingthe parameter set {PCI, Δ_(ss), c_(init) ^(CSH)} to Equations 1 to 14.Here, since the PCI corresponds to N_(ID) ^(cell), the above descriptionof Equations 1 to 14 can be equally applied and thus redundantdescription is omitted for clarity.

Scheme A-2

In addition, a UL RS generation operation of the UE, proposed by thepresent invention, when VCI and CSH pattern seed values are provided tothe UE will now be described.

For example, {VCI(m), c_(init) ^(CSH) (m)} (m=0, 1, 2, . . . ) may beprovided to the UE at a specific time through UE-specific higher layersignaling (e.g. RRC signaling). Here, m is a parameter set index. Forexample, when M PUCCH DMRS setting sets are present and m indicates oneof the M sets, m can have one of values of 0 to M−1. If L PUSCH DMRSsetting sets are present and m indicates one of the L sets, m can haveone of values of M, M+1, . . . , M+L−1. When N SRS setting sets arepresent and m indicates one of the N sets, m can have one of values ofM+L, M+L+1, . . . , M+L+N−1.

Here, a plurality of sets of {VCI(m), c_(init) ^(CSH) (m)} can besemi-statically provided through higher layer signaling, and the valueof the specific index m indicating one of the sets, which will be usedby the UE, can be dynamically signaled (e.g. L1/L2 signaled).

It is assumed that the number of PUCCH DMRS setting sets is M=1 in thefollowing description. That is, while a plurality of PUCCH DMRS settingsets can be given and one of the sets can be dynamically switched andapplied, it is assumed that a VCI for PUCCH DMRS generation isdetermined as VCI^(PUCCH)=VCI(0) and a seed value for a CSH pattern ofthe PUCCH DMRS is determined as c_(init) ^(CSH) ^(_) ^(PUCCH)=c_(init)^(CSH) (0) using a set {VCI(0), c_(init) ^(CSH) (0)} corresponding to asemi-statically set index m=0 for the PUCCH DMRS in the followingdescription. Here, semi-static setting of {VCI(0), c_(init) ^(CSH) (0)}corresponding to m=0 means that {VCI(0), c_(init) ^(CSH) (0)} can bechanged at a relatively long interval. Since a PUCCH is a controlchannel for stably carrying UCI, semi-static DMRS sequence change can bepreferable. However, the present invention does not exclude provision ofUE-specific higher layer signaling to set a PUCCH DMRS according to ascheme using M of larger than 2.

According to a conventional scheme, c_(init) ^(CSH) for a PUCCH DMRS wasdefined as c_(init) ^(CSH) ^(_) ^(PUCCH)=PCI. When VCI^(PUCCH) isprovided to the UE, the present invention provides c_(init) ^(CSH) ^(_)^(PUCCH) defined separately (or independently) of VCI^(PUCCH) throughUE-specific higher layer signaling, instead of determining c_(init)^(CSH) ^(_) ^(PUCCH) as c_(init) ^(CSH) ^(_) ^(PUCCH)=VCI^(PUCCH)according to the conventional scheme. Accordingly, even when differentvalues of VCI^(PUCCH) are set for MU-MIMO-paired UEs (the same basesequence can be determined even if different values of VCI^(PUCCH) areset), an OCC can be applied to DMRSs of the paired UEs to provideorthogonality by setting the same c_(init) ^(CSH) ^(_) ^(PUCCH). Thatis, according to the present invention, VCI^(PUCCH) and c_(init) ^(CSH)^(_) ^(PUCCH), which are independent parameters, can be set throughUE-specific higher layer signaling, and thus MU-MIMO pairing(particularly, inter-cell UE pairing) using an OCC can be supported.

An operation of the UE to generate a UL RS when M=1 (i.e. the number ofPUCCH DMRS setting sets is 1) and L=1 (i.e. the number of PUSCH DMRSsetting sets is 1) will now be described. The following description isfor clarity and the present invention can be equally applied to cases inwhich one or more of M, L and N have a value larger than 1.

Scheme A-2-i

When M=1 and L=1, {VCI(0), c_(init) ^(CSH) (0)} is defined as a PUCCHparameter set, as described above. Provision of c_(init) ^(CSH) (0)through higher layer signaling may mean that a PUCCH CSH pattern needsto be determined using c_(init) ^(CSH) (0) explicitly providedindependently of VCI(0). In this case, dynamic indication (or dynamicswitching) between the PCI basically provided to the UE and the VCI(0)may be signaled through a specific DCI format.

When c_(init) ^(CSH) (0) is not provided through higher layer signalingand only VCI(0) is provided, c_(init) ^(CSH) ^(_) ^(PUCCH) can bedetermined as c_(init) ^(CSH) ^(_) ^(PUCCH)=VCI(0). In this case,dynamic indication between the PCI and VCI(0) may be signaled through aspecific DCI format.

Here, {VCI(1), c_(init) ^(CSH) (1)} is defined as a PUSCH DMRS parameterset because L=1. Provision of c_(init) ^(CSH) (1) through higher layersignaling may mean that a PUSCH CSH pattern needs to be determined usingc_(init) ^(CSH) (1) explicitly given independently of VCI(1) instead ofbeing based on VCI(1) as in the conventional method. In this case,dynamic indication between PUSCH parameter set {VCI(1), c_(init) ^(CSH)(1)} proposed by the present invention and the legacy parameter set{PCI, Δ_(ss), c_(init) ^(CSH)} may be signaled through uplink-relatedDCI.

Scheme A-2-ii

This scheme represents application of the scheme A-2-i as a mathematicalexpression when M=1 and L=1. That is, the following embodiments of thepresent invention can be regarded as schemes for supporting generationof a UL RS having backward compatibility with the legacy system in termsof UE operation. That is, in a system defining 3GPP LTE release-10,forms or calculation processes of equations (refer to descriptionrelated to Equations 1 to 14) used for the UE to generate a UL RS aremaintained without change and parameters applied to the equations arereplaced by VCI(m), f_(ss) ^(PUCCH)(m), c_(init) ^(CSH) (m), etc.proposed by the present invention.

Specifically, the group hopping pattern f_(gh)(n_(s)) for a PUSCH and aPUCCH is defined as in Equation 3. However, the pseudo-random sequencec(i) can be defined such that it is initialized to

$c_{init} = \left\lfloor \frac{{VCI}(m)}{30} \right\rfloor$at the start of each radio frame by modifying Equation 6. Here, VCI(0)may correspond to the first VCI for the PUCCH and VCI(1) may correspondto the second VCI for the PUSCH.

The sequence shift pattern f_(ss) may be defined separately for thePUCCH and PUSCH. f_(ss) ^(PUCCH) for the PUCCH (i.e. m=0) can bedetermined as f_(ss) ^(PUCCH) (m)=VCI(m)mod 30 by modifying Equation 7and f_(ss) ^(PUSCH) for the PUSCH (i.e. m=1) can be determined as f_(ss)^(PUSCH) (m)=(f_(ss) ^(PUCCH) (m)+Δ_(ss))mod 30 by modifying Equation 8.Here, Δ_(ss)ε{0, 1, . . . ,29}, which can be set by a higher layer.

While sequence hopping is applied only to RSs corresponding to M_(sc)^(RS)≧6N_(sc) ^(RB) as in the conventional scheme, the pseudo-randomsequence generator with respect to sequence hopping can be defined suchthat it is initialized to

$c_{init} = {{\left\lfloor \frac{{VCI}(m)}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}$at the start of each radio frame by modifying Equation 9.

A cyclic shift value α_(λ) for the PUSCH (that is, m=1) in slot n_(s) isgiven as α_(λ)=2πn_(cs,λ)/12 where n_(cs,λ)=(n_(DMRS) ⁽¹⁾+n_(DMRS)⁽²⁾+n_(PN)(n_(s)))mod12, as described with reference to Table 3. Here, apseudo-random sequence generator for n_(PN)(n_(s)) may be defined suchthat it is initialized at the start of each radio frame according to

$c_{init}^{CSH\_ PUSCH} = {{\left\lfloor \frac{V\; C\;{I(m)}}{30} \right\rfloor \cdot 2^{5}} + f_{ss}^{PUSCH}}$or initialized according to c_(init) ^(CSH) ^(_) ^(PUSCH)=c_(init)^(CSH) (m) modifying Equation 13.

In addition, all PUCCH (i.e. m=0) formats use the cell-specific CS,n_(cs) ^(cell) (n_(s),l). cell n_(cs) ^(cell)(n_(s),l) has differentvalues according to a symbol number l and slot number n_(s) and isdetermined according to n_(cs) ^(cell)(n_(s),l)=Σ_(i=0) ⁷c(8N_(symb)^(UL)·n_(s)+8l+i)·2^(i). Here, the pseudo-random sequence c(i) can bedefined such that it is initialized at the start of each radio frameaccording to c_(init) ^(CSH) ^(—PUCCH) =VCI(m) or c_(init) ^(CSH) ^(_)^(PUCCH)=c_(init) ^(CSH) (m)

Scheme A-2-iii

It is assumed that M=1 and L=1 as described in the A-2-i and A-2-iischemes. According to the present scheme, a base sequence generated bythe UE is identical to a base sequence generated by a UE′ of a targetcell. Particularly, the present scheme relates to a method ofdetermining a VCI such that the base sequence generated by the UE isidentical to the base sequence generated by the UE′ of the target cellwhile a network signals only the VCI to the UE through higher layersignaling. For example, when a specific cell signals the PUSCH VCI(1) tothe UE through higher layer signaling, if the UE′ of the target celluses PCI′ and Δ_(ss)′ provided by the target cell and a base sequence ofthe UE′, which is generated according to f_(ss) ^(PUCCH)′=PCI′ mod 30and f_(ss) ^(PUSCH)′=(f_(ss) ^(PUCCH)′+Δ_(ss)′)mod30 is present, VCI(1)can be determined as follows.

$\begin{matrix}{{V\; C\;{I(1)}} = {\left( {30 \times \left\lfloor \frac{P\; C\; I^{\prime}}{30} \right\rfloor} \right) + f_{ss}^{PUSCH}}} & \left\lbrack {{Equation}\mspace{14mu} 27} \right\rbrack\end{matrix}$

In addition, f_(ss) ^(PUSCH) can be arranged as Equation 28.

$\begin{matrix}\begin{matrix}{f_{ss}^{PUSCH} = {\left( {f_{ss}^{{PUSCH}^{\prime}} + 30 - \Delta_{ss}} \right){mod}\; 30}} \\{= {\left( {f_{ss}^{{PUCCH}^{\prime}} + \Delta_{ss}^{\prime} + 30 - \Delta_{ss}} \right){mod}\; 30}} \\{= {\left( {f_{ss}^{{PUCCH}^{\prime}} + \Delta_{ss}^{\prime} - \Delta_{ss}} \right){mod}\; 30}}\end{matrix} & \left\lbrack {{Equation}\mspace{14mu} 28} \right\rbrack\end{matrix}$

When Equation 28 is applied to Equation 27, the following equation isobtained.

$\begin{matrix}{{V\; C\;{I(1)}} = {\left( {30 \times \left\lfloor \frac{P\; C\; I^{\prime}}{30} \right\rfloor} \right) + {\left( {f_{ss}^{{PUCCH}^{\prime}} + \Delta_{ss}^{\prime} - \Delta_{ss}} \right){mod}\; 30}}} & \left\lbrack {{Equation}\mspace{14mu} 29} \right\rbrack\end{matrix}$

When the eNB provides the value of VCI(1), determined according toEquation 29, to the UE, the UE can generate the same base sequence asthat of the UE′ of the specific target cell.

The meaning of the above equation is as follows. f_(ss) ^(PUSCH)′ of thecell to which the UE′ belongs equals (f_(ss) ^(PUCCH)′+Δ_(ss)′)mod30 and

f_(ss)^(PUCCH ′) = P C I^(′)mod 30.$30 \times \left\lfloor \frac{P\; C\; I^{\prime}}{30} \right\rfloor$can be determined such that it has the same value as the integer part(or quotient) of

$\frac{P\; C\; I^{\prime}}{30}$of the target cell to which the UE′ belongs. In addition, (f_(ss)^(PUCCH)′+Δ_(ss)′−Δ_(ss))mod 30 can be determined such that it has thesame value as the modulo part (or remainder) of

$\frac{P\; C\; I^{\prime}}{30}$of the target cell to which the UE′ belongs in order to consider Δ_(ss)′used by the target cell and to previously eliminate Δ_(ss) used as acell-specific value in the cell to which the UE belongs. When VCI(1)determined according to Equation 29 is signaled to the UE, the UEcalculates f_(ss) ^(PUSCH) according to f_(ss)^(PUSCH)=({VCI(1)mod30}+Δ_(ss))mod 30 only by replacing n_(ID) ^(cell)by VCI(1) while using Equations 7 and 8. Here, when the UE calculatesf_(ss) ^(PUSCH), Δ_(ss) is eliminated and Δ_(ss)′ is left and thus theUE can generate the same base sequence as that of the UE′.

The above description of the scheme of setting a VCI for the UE of thespecific cell such that the UE generates the same base sequence as thatof the UE′ of the target cell is exemplary. That is, variousmodifications or modified equations for determining a modulo part of aVCI according to the scheme of previously eliminating Δ_(ss) of a cellto which a CoMP UE belongs and the scheme of reflecting Δ_(ss)′ of thetarget cell are within the scope of the present invention.

Scheme B

Scheme B is applicable to the A-UE which is not limited to theconventional calculation method, according to the conventional scheme(e.g. scheme described with reference to Equations 1 to 14) or a schemeof newly defining only parameters of the conventional scheme.

Scheme B-1

The UE can acquire a parameter set {PCI, Δ_(ss), c_(init) ^(CSH)} in aninitial access procedure and thus generate a UL RS sequence. Here, PUCCHDMRS, PUSCH DMRS and SRS sequences can be generated by applying theparameter set {PCI, Δ_(ss), c_(init) ^(CSH)} to Equations 1 to 14, asdescribed in scheme A-1.

Scheme B-2

In addition, a UL RS generation operation of the UE when the UE receives{VCI(m), c_(init) ^(CSH) (m)} (m=0, 1, 2, . . . ) at a specific timethrough UE-specific higher layer signaling (e.g. RRC signaling) isdescribed below.

Scheme B-2-i

A UL RS generation operation of the UE on the assumption that M=1 (i.e.the number of PUCCH DMRS setting sets is 1) and L=1 (i.e. the number ofPUSCH DMRS setting sets is 1) may be identical to that described in thescheme A-2-i. However, the principle of the present invention can beequally applied to cases in which one of M, L and N has a value oflarger than 1.

Scheme B-2-ii

This scheme represents application of the scheme B-2-i as a mathematicalexpression when M=1 and L=1. That is, the following embodiments of thepresent invention relate to schemes defined differently from UEoperation according to the legacy system. That is, the followingembodiments relate to a method of calculating base sequence generationin a manner different from the conventional method rather than a methodof using the conventional scheme (scheme described with reference toEquations 1 to 14) or newly defining (or replacing) only a parameter inthe conventional scheme.

Specifically, the group hopping pattern f_(gh)(n_(s)) for a PUSCH and aPUCCH is defined as in Equation 3. However, the pseudo-random sequencec(i) can be defined such that it is initialized to

$c_{init} = \left\lfloor \frac{V\; C\;{I(m)}}{30} \right\rfloor$at the start of each radio frame by modifying Equation 6. Here, VCI(0)may correspond to the first VCI for the PUCCH and VCI(1) may correspondto the second VCI for the PUSCH.

The sequence shift pattern f_(ss) may be defined separately for thePUCCH and PUSCH. f_(ss) ^(PUCCH) for the PUCCH (i.e. m=0) can bedetermined as f_(ss) ^(PUCCH)(m)=VCI(m)mod 30 by modifying Equation 7.f_(ss) ^(PUSCH) for the PUSCH (i.e. m=1) can be determined as f_(ss)^(PUSCH) (m)=VCI(m)mod 30, different from Equation 8. That is, even ifVCI(0) for the PUCCH and VCI(1) for the PUSCH are different from eachother, f_(ss)(m) for the PUCCH and PUSCH can be commonly defined asf_(ss)(m)=VCI(m)mod 30.

While sequence hopping is applied only to RSs corresponding to M_(sc)^(RS)≧6N_(sc) ^(RB) as in the conventional scheme, the pseudo-randomsequence generator with respect to sequence hopping can be defined suchthat it is initialized to

$c_{init} = {{\left\lfloor \frac{V\; C\;{I(m)}}{30} \right\rfloor \cdot 2^{5}} + {f_{ss}(m)}}$at the start of each radio frame by modifying Equation 9.

A cyclic shift value α_(λ) for the PUSCH (that is, m=1) in slot n_(s) isgiven as α_(λ)=2πn_(cs,λ)/12 where n_(cs,λ)=(n_(DMRS) ⁽¹⁾+n_(DMRS,λ)⁽²⁾+n_(PN)(n_(s)))mod12, as described with reference to Table 3. Here, apseudo-random sequence generator for n_(PN)(n_(s)) may be defined suchthat it is initialized at the start of each radio frame according to

$c_{init}^{CSH\_ PUSCH} = {{\left\lfloor \frac{V\; C\;{I(m)}}{30} \right\rfloor \cdot 2^{5}} + {f_{ss}(m)}}$or initialized according to c_(init) ^(CSH) ^(_) ^(PUSCH)=c_(init)^(CSH) (m) by modifying Equation 13.

In addition, all PUCCH (i.e. m=0) formats use the cell-specific CS,n_(cs) ^(cell)(n_(s),l). n_(cs) ^(cell)(n_(s),l) has different valuesaccording to a symbol number l and slot number n_(s) and is determinedaccording to n_(cs) ^(cell) (n_(s),l)=Σ_(i=0) ⁷c(8N_(symb)^(UL)·n_(s)+8l+i)·2^(i). Here, the pseudo-random sequence c(i) can bedefined such that it is initialized at the start of each radio frameaccording to C_(init) ^(CSH) ^(_) ^(PUCCH)=VCI(m) or c_(init) ^(CSH)^(_) ^(PUCCH)=c_(init) ^(CSH) (m)

According to the scheme B-2-ii, the UL RS sequence generation operationof the UE can be simplified and optimized. For example, a newcalculation method for determining the sequence shift pattern f_(ss)according to f_(ss)(m)=VCI(m)mod 30 is provided. That is, if VCI(m) isprovided through RRC signaling, the operation may be represented on theassumption that Δ_(ss)=0 all the time. In other words, the cell-specificvalue Δ_(ss) previously provided to the UE (i.e. previously set by ahigher layer) is not used any more after the UE receives VCI(m).

Scheme B-2-iii

It is assumed that M=1 and L=1 as described in the B-2-i and B-2-iischemes. According to the present scheme, a base sequence generated bythe UE is identical to a base sequence generated by a UE′ of a targetcell. Particularly, the present scheme relates to a method ofdetermining a VCI such that the base sequence generated by the UE isidentical to the base sequence generated by the UE′ of the target cellwhile a network signals only the VCI to the UE through higher layersignaling. For example, when a specific cell signals the PUSCH VCI(1) tothe UE through higher layer signaling, if the UE′ of the target celluses PCI′ and Δ_(ss)′ provided by the target cell and a base sequence ofthe UE′, which is generated according to f_(ss) ^(PUCCH)′=PCI′ mod 30and f_(ss) ^(PUSCH)′=(f_(ss) ^(PUCCH)′+Δ_(ss)′)mod 30 is present, VCI(1)can be determined as follows.

$\begin{matrix}\begin{matrix}{{V\; C\;{I(1)}} = {\left( {30 \times \left\lfloor \frac{P\; C\; I^{\prime}}{30} \right\rfloor} \right) + f_{ss}^{PUSCH}}} \\{= {\left( {30 \times \left\lfloor \frac{P\; C\; I^{\prime}}{30} \right\rfloor} \right) + {f_{ss}(m)}}} \\{= {\left( {30 \times \left\lfloor \frac{P\; C\; I^{\prime}}{30} \right\rfloor} \right) + {V\; C\;{I(1)}{mod}\; 30}}}\end{matrix} & \left\lbrack {{Equation}\mspace{14mu} 30} \right\rbrack\end{matrix}$

When the eNB provides the value of VCI(1), determined according toEquation 30, to the UE, the UE can generate the same base sequence asthat of the UE′ of the specific target cell.

The meaning of the above equation is described. f_(ss) ^(PUSCH)′ of thecell to which the UE′ belongs equals (f_(ss) ^(PUCCH)′+Δ_(ss)′)mod 30and

f_(ss)^(PUCCH ′) = P C I^(′)mod 30.$30 \times \left\lfloor \frac{P\; C\; I^{\prime}}{30} \right\rfloor$can be determined such that it has the same value as the integer part(or quotient) of

$\frac{P\; C\; I^{\prime}}{30}$of the target cell to which the UE′ belongs. In addition, f_(ss)^(PUSCH)′ is determined in consideration of only Δ_(ss)′ (that is, UEassumes Δ_(ss)=0 all the time) used in the target cell such that f_(ss)^(PUSCH)′ has the same value as the modulo part (or remainder) of

$\frac{P\; C\; I^{\prime}}{30}$of the target cell to which the UE′ belongs. When VCI(1) determinedaccording to Equation 30 is signaled to the UE, the UE can simplycalculate f_(ss) according to f_(ss)(m)=VCI(1)mod 30 and can generatethe same base sequence as that of the UE′ because Δ_(ss)′ has beenreflected in f_(ss).

The above description of the scheme of setting a VCI for the UE of thespecific cell such that the UE generates the same base sequence as thatof the UE′ of the target cell is exemplary. That is, variousmodifications or modified equations for determining a modulo part of aVCI according to the scheme of reflecting only Δ_(ss)′ of the targetcell.

In the embodiments for describing the schemes A and B, M, L and N may bearbitrary values and, when each of M, L and N is larger than 1, aspecific one of a plurality of RS setting parameter sets correspondingthereto can be dynamically indicated (dynamically switched) through aDCI format.

When N for SRS sequence generation is larger than 1, the CoMP UE cangenerate a plurality of SRS sequences. Furthermore, even if M, L and Nare larger than 1, the cell-specific parameter set (i.e. {PCI, Δ_(ss),c_(init) ^(CSH)}) of the corresponding cell, which is initially acquiredby the UE, can be included in the dynamically indicated RS settingparameter sets such that the cell-specific parameter set is applied as adefault set (i.e. applied in the form of a fall-back mode).

VCI Subdivision Scheme

The above-mentioned embodiments of the present invention have describedthe scheme of using a common VCI for a PUCCH and a PUSCH and the schemeof respectively using separate VCIs for the PUCCH and PUSCH when a UL RSbase sequence is generated using a VCI.

Additionally, the present invention proposes a scheme of setting andusing an independent (or separate) VCI for subdivided purposes.

For example, subdivided VCIs can be set in such manner that individualVCIs are respectively used for group hopping, sequence shift, sequencehopping, and cyclic shift hopping (CSH) when a PUSCH DMRS base sequenceis generated. Otherwise, subdivided VCIs can be set in such a mannerthat group hopping, sequence shift, sequence hopping and CSH operationsare grouped into one or more groups and each group uses a common VCI.For example, group hopping/sequence hopping and sequence shift can use acommon VCI and CSH can use a separate VCI_(CSH) (or N_(ID) ^(csh) ^(_)^(DMRS)). VCIs subdivided in this manner may be set through higher layersignaling (e.g. RRC signaling) and each subdivided VCI may have a rangeof 0 to 509.

Alternatively, subdivided VCIs can be set in such a manner that grouphopping for a PUSCH, group hopping for a PUCCH, sequence shift for thePUSCH, sequence shift for the PUCCH, sequence hopping for the PUSCH,sequence hopping for the PUCCH, CSH for the PUSCH and CSH for the PUCCHcan be grouped into one or more groups and each group can use a commonVCI.

For example, the same VCI (e.g. N_(ID) ^((PUSCH))ε{0, . . . , 509}) canbe commonly applied to Equation 18 (i.e. group hopping for each of aPUSCH and a PUCCH), Equation 20 (i.e. sequence shift for a PUCCH) andEquation 23 (i.e. the first or second scheme for sequence shift for aPUSCH). A separate VCI (e.g. N_(ID,seq) ^((PUSCH))ε{0, . . . , 509}) canbe set and used for Equation 25 (i.e. sequence hopping for a PUSCH) togenerate an independent sequence hopping pattern, providing additionalDMRS flexibility. Furthermore, another separate VCI (e.g. N_(ID,seq)^((PUSCH))ε{0, . . . , 509} or N_(ID) ^(csh) ^(_) ^(DMRS)ε{0, . . . ,509}) may be set and used for Equation 26 (i.e. CSH for a PUSCH) togenerate an independent CSH to provide additional DMRS flexibility suchas inter-cell MU-MIMO.

Alternatively, the same VCI (e.g. N_(ID) ^((PUSCH))ε{0, . . . , 509})can be commonly applied to Equation 18, Equation 20, Equation 23 (orEquation 16) and Equation 25, whereas a separate VCI (e.g. N_(ID,CSH)^((PUSCH))ε{0, . . . , 509} or N_(ID) ^(csh) ^(_) ^(DMRS)ε{0, . . . ,509}) is set and used only for Equation 26 (i.e. CSH for a PUSCH) togenerate independent CSH. In this case, Equation 26 can be modified intoEquation 31.

$\begin{matrix}{{c_{init} = {{\left\lfloor \frac{N_{{ID},{CSH}}^{({PUSCH})}}{30} \right\rfloor \cdot 2^{5}} + \left( {N_{{ID},{CSH}}^{({PUSCH})}{mod}\; 30} \right)}}{or}{c_{init} = {{\left\lfloor \frac{N_{ID}^{csh\_ DMRS}}{30} \right\rfloor \cdot 2^{5}} + \left( {N_{ID}^{csh\_ DMRS}{mod}\; 30} \right)}}} & \left\lbrack {{Equation}\mspace{14mu} 31} \right\rbrack\end{matrix}$

When a parameter used for CSH is set separately from parameters used forother operations (e.g. group hopping/sequence hopping and/or sequenceshift) for generating a base sequence as represented by Equation 31, thePCI needs to be replaced by a VCI (i.e. N_(ID,CSH) ^((PUSCH)) or N_(ID)^(csh) ^(_) ^(DMRS)) and f_(ss) ^(PUSCH) needs to be calculated inconsideration of the VCI (i.e. N_(ID,CSH) ^((PUSCH)) or N_(ID) ^(csh)^(_) ^(DMRS)) in Equation 13 (i.e. the conventional scheme for aninitial value of a pseudo-random sequence).

Here, one of the first, second and third schemes for setting Δ_(ss) canbe used to calculate f_(ss) ^(PUSCH) as described above with referenceto Equation 23 or Equation 16. Equation 31 corresponds to a case inwhich N_(ID) ^((PUSCH)) in f_(ss) ^(PUSCH)=N_(ID) ^((PUSCH))mod 30 isreplaced by N_(ID,CSH) ^((PUSCH)) (or N_(ID) ^(csh) ^(_) ^(DMRS)).

In case of sequence hopping, one of the first, second and third schemesfor setting Δ_(ss) can be used to calculate f_(ss) ^(PUSCH) of Equation25, and a subdivided VCI (e.g. one of N_(ID) ^((PUSCH)), N_(ID,seq)^((PUSCH)) and N_(ID,CSH) ^((PUSCH))) can be applied.

If the UE receives only one value of N_(ID) ^((PUSCH)) throughUE-specific higher layer signaling, a base sequence can be generatedusing the same value of N_(ID) ^((PUSCH)) for Equation 18, Equation 20,Equation 23 (or Equation 16), Equation 25 and Equation 26.

If the UE receives a parameter set {N_(ID) ^((PUSCH)), N_(ID) ^(csh)^(_) ^(DMRS)} through higher layer signaling at a specific time, thesame value of N_(ID) ^((PUSCH)) may be used for Equation 18, Equation20, Equation 23 (or Equation 16) and Equation 25, whereas N_(ID) ^(csh)^(_) ^(DMRS) may be used (or dynamic switching between using of N_(ID)^(csh) ^(_) ^(DMRS) and using of N_(ID) ^((PUSCH)) may be applied) forthe CSH pattern of Equation 26. Dynamic switching may include indicationof a parameter to be used from among parameters previously set throughhigher layer signaling using a specific field of a DCI format.

If the UE receives a parameter set {N_(ID) ^((PUSCH)), N_(ID,seq)^((PUSCH))} through higher layer signaling, the same value of N_(ID)^((PUSCH)) may be used for Equation 18, Equation 20, Equation 23 (orEquation 16) and Equation 26, whereas N_(ID,seq) ^((PUSCH)) may be used(or dynamic switching between using of N_(ID,seg) ^((PUSCH)) using ofN_(ID) ^((PUSCH)) may be applied) for the sequence hopping pattern ofEquation 25.

If the UE receives a parameter set {N_(ID) ^((PUSCH)), N_(ID,seq)^((PUSCH)), N_(ID) ^(csh) ^(_) ^(DMRS)} through higher layer signalingat a specific time, the same value of N_(ID) ^((PUSCH)) may be used forEquation 18, Equation 20 and Equation 23 (or Equation 16), N_(ID,seq)^((PUSCH)) may be used (or dynamic switching between using of N_(ID,seq)^((PUSCH)) and using of N_(ID) ^((PUSCH)) may be applied) for thesequence hopping pattern of Equation 25, and N_(ID) ^(csh) ^(_) ^(DMRS)may be used (or dynamic switching between using of N_(ID) ^(csh) ^(_)^(DMRS) and using of N_(ID) ^((PUSCH)) may be applied) for the CSHpattern of Equation 26.

Method for Dynamically Signaling VCI Used to Generate DMRS Sequence

As described in the aforementioned embodiments of the present invention,when VCIs are used for generation of a UL DMRS sequence, it is desirableto dynamically indicate a VCI used to generate a UL DMRS in order toprovide UE scheduling flexibility.

For example, a plurality of PUSCH DMRS VCI values N_(ID) ^((PUSCH)) orn_(ID) ^((PUSCH)) may be set by a higher layer and a value to be usedfrom among the plurality of PUSCH DMRS VCI values N_(ID) ^((PUSCH)) orn_(ID) ^((PUSCH)) may be dynamically indicated through uplink schedulinggrant information (that is, uplink-related DCI). Here, when the PUSCHDMRS VCI values N_(ID) ^((PUSCH)) or n_(ID) ^((PUSCH)) are set by thehigher layer, specific values Δ_(ss) (i.e., basic sequence index offsetsbetween base sequences of PUCCH DMRS and PUSCH DMRS when the same cellID is applied to generation of the basic sequences of PUCCH DMRS andPUSCH DMRS (refer to Equation 8)) respectively mapped to the PUSCH DMRSVCI values may be used.

To dynamically indicate one of the PUSCH DMRS VCI values N_(ID)^((PUSCH)) or n_(ID) ^((PUSCH)) through the uplink-related DCI, a bit(or bits) for indicating a virtual cell ID may be newly added to theuplink-related DCI format to explicitly indicate the corresponding VCIor an existing bit (or bits) may be reused. For example, a mappingrelationship can be established such that one of states of a 3-bit“Carrier Indicator” field or a 3-bit “Cyclic Shift for DMRS and OCCindex” field from among bit fields of the uplink-related DCI (e.g. DCIformat 0 or 4) implicitly indicates one of the PUSCH DMRS VCI valuesN_(ID) ^((PUSCH)) or n_(ID) ^((PUSCH)).

A description will be given of a method for indicating one of aplurality of VCIs (e.g. PUSCH DMRS N_(ID) ^((PUSCH)) or n_(ID)^((PUSCH))) using the 3-bit “Cyclic Shift for DMRS and OCC index” field(referred to as “DMRS_CS” field hereinafter) defined in theuplink-related DCI format (e.g. DCI format 0 or 4), suggested by thepresent invention.

A parameter set including VCI, Δ_(ss) and/or c_(init) ^(CSH), asdescribed in the aforementioned embodiments of the present invention,may be provided as UE-specific higher layer parameters with respect toPUSCH DMRS. While it is assumed that one parameter set includes {VCI,c_(init) ^(CSH)} since Δ_(ss) is set to 0 in the present embodiment, thescope of the present invention is not limited thereto and variousparameter sets can be set according to the aforementioned embodiments.

When N PUSCH DMRS parameter sets are determined by the higher layer(that is, when N parameter set candidates are determined) and oneparameter set is defined as S_(n), S_(n) may be represented asS_(n)={VCI_(n), c_(init,n) ^(CSH)} (n=1, 2, . . . , N). That is, aparameter set to be used for PUSCH DMRS generation, from among the Nparameter sets {S₁, S₂, . . . , S_(N)}, may be implicitly or dynamicallyindicated through the “DMRS_CS” field of the uplink-related DCI.

In the method of indicating a specific parameter set from among the Nparameter sets, which are determined by the higher layer for PUSCH DMRSsequences, using the DMRS_CS field, the present invention can maximize aCS distance (i.e., increase CS orthogonality) for the N parameter setsin cyclic shift values applied to sequences using the correspondingparameter set. Particularly, according to methods provided by thepresent invention, in case of MU-MIMO pairing of a plurality of UEs eachof which uses a maximum of 2 layers (i.e. λ=0, 1), it is possible tomaximize a CS distance between UEs while using the same parameter setfor PUSCH DMRS sequence generation.

The following table 4 shows an example of the present invention, whichdefines an implicit mapping relationship between states of the “DMRS_CS”field and parameter sets when N=2.

TABLE 4 n_(DMRS, λ) ⁽²⁾ [w^((λ))(0) w^((λ))(1)] Option DMRS_CS λ = 0 λ =1 λ = 2 λ = 3 λ = 0 λ = 1 λ = 2 λ = 3 a b c d 000 0 6 3 9 [1 1] [1 1] [1−1] [1 −1] S₁ S₁ S₁ S₁ 001 6 0 9 3 [1 −1] [1 −1] [1 1] [1 1] S₁ S₁ S₁ S₁010 3 9 6 0 [1 −1] [1 −1] [1 1] [1 1] S₁ S₁ S₂ S₂ 011 4 10 7 1 [1 1] [11] [1 1] [1 1] S₂ S₁ S₂ S₂ 100 2 8 5 11 [1 1] [1 1] [1 1] [1 1] S₂ S₂ S₁S₂ 101 8 2 11 5 [1 −1] [1 −1] [1 −1] [1 −1] S₂ S₂ S₁ S₂ 110 10 4 1 7 [1−1] [1 −1] [1 −1] [1 −1] S₂ S₂ S₂ S₁ 111 9 3 0 6 [1 1] [1 1] [1 −1] [1−1] S₁ S₂ S₂ S₁

A cyclic shift value for a PUSCH is provided as α_(λ)=2πn_(cs,λ)/12 in aslot n_(s) and n_(cs,λ)=(n_(DMRS) ⁽¹⁾n_(DMRS,λ) ⁽²⁾+n_(PN)(n_(s)))mod 12is defined (refer to the part above Table 3). Table 4 shows that the “CSfor DMRS” field in the uplink-related DCI format indicates n_(DMRS,λ)⁽²⁾, OCC of [w^((λ))(0) w^((λ))(1)] and a DMRS generation parameter set(e.g. first set S₁ or second set S₂) from among parameters used forcyclic shift determination.

In the example as shown in Table 4, S₁ and may be implicitly mapped to 4states and S₂ may also be implicitly mapped to 4 states such that S₁ andS₂ are respectively mapped to halves of 3 bits (i.e. 8 states) ofDMRS_CS(n_(DMRS,λ) ⁽²⁾). Four options a, b, c and d as shown in Table 4are provided as methods for mapping each parameter set to 4 states.

Option a maps 4 states for S₁ such that a CS distance in n_(DMRS,λ) ⁽²⁾values is maximized. That is, S₁ is mapped to states 000, 001, 010 and111 of the DMRS_CS field in Table 4, and the states are respectivelymapped to n_(DMRS,λ) ⁽²⁾=0, 6, 3, 9 when λ=0. Accordingly, a minimum CSdistance in the values respectively corresponding to the states becomes3. When λ=1, the states are respectively mapped to n_(DMRS,λ) ⁽²⁾=6, 0,9, 3 and thus the minimum CS distance becomes 3. In case of λ=2 and λ=3,the minimum CS distance also becomes 3. Accordingly, the CS distance inthe 4 states of the DMRS_CS field can be at least 3 for UEs using thesame parameter set S₁ for DMRS generation. In a length-12 DMRS sequence,a CS distance of at least 3 in sequences respectively used by 4 UEscorresponds to a maximum CS distance. It can be considered thatorthogonality between sequences increases as CS distance increases.Accordingly, MU-MIMO pairing according to CS orthogonality between UEsusing the same parameter set can be effectively performed.

In addition, according to option a, the other parameter set S₂ is mappedto states 011, 100, 101 and 110 of the DMRS_CS field. The states arerespectively mapped to n_(DMRS,λ) ⁽²⁾=4, 2, 8, 10 when λ=0 and thus aminimum CS distance becomes 2. When λ=1, the states are respectivelymapped to n_(DMRS,λ) ⁽²⁾=10, 8, 2, 4 and thus the minimum CS distancebecomes 2. In case of λ=2 and λ=3, the minimum CS distance also becomes2. Accordingly, the minimum CS distance in the four states of theDMRS_CS field becomes 2 for UEs using the same parameter set S₂ so thatorthogonality can be improved according to maximization of the CSdistance.

While CS orthogonality when S₂ is used may be considered to berelatively low because the CS distance when S₂ is used is less than thatwhen S₁ is used, maximum CS distances are provided for the two parametersets S₁ and S₂ considering that CS distances cannot be respectively setfor the two parameter sets S₁ and S₂.

In options b, c and d of Table 4, a specific set from among the multipleparameter sets may be indicated using the DMRS_CS field in theuplink-related DCI format, and a CS distance in sequences may bemaximized even when the same parameter set is applied.

The following table 5 shows another example with respect to the methodfor dynamically signaling a DMRS parameter set according to the presentinvention.

TABLE 5 n_(DMRS, λ) ⁽²⁾ [w^((λ))(0) w^((λ))(1)] Option DMRS_CS λ = 0 λ =1 λ = 2 λ = 3 λ = 0 λ = 1 λ = 2 λ = 3 e f g h 000 0 6 3 9 [1 1] [1 1] [1−1] [1 −1] S₁ S₁ S₁ S₁ 001 6 0 9 3 [1 −1] [1 −1] [1 1] [1 1] S₂ S₂ S₂ S₂010 3 9 6 0 [1 −1] [1 −1] [1 1] [1 1] S₂ S₂ S₂ S₂ 011 4 10 7 1 [1 1] [11] [1 1] [1 1] S₂ S₁ S₁ S₂ 100 2 8 5 11 [1 1] [1 1] [1 1] [1 1] S₂ S₁ S₂S₁ 101 8 2 11 5 [1 −1] [1 −1] [1 −1] [1 −1] S₁ S₂ S₁ S₂ 110 10 4 1 7 [1−1] [1 −1] [1 −1] [1 −1] S₁ S₂ S₂ S₁ 111 9 3 0 6 [1 1] [1 1] [1 −1] [1−1] S₁ S₁ S₁ S₁ n_(DMRS, λ) ⁽²⁾ [w^((λ))(0) w^((λ))(1)] Option DMRS_CS λ= 0 λ = 1 λ = 2 λ = 3 λ = 0 λ = 1 λ = 2 λ = 3 i j k l 000 0 6 3 9 [1 1][1 1] [1 −1] [1 −1] S₁ S₁ S₁ S₁ 001 6 0 9 3 [1 −1] [1 −1] [1 1] [1 1] S₁S₁ S₁ S₁ 010 3 9 6 0 [1 −1] [1 −1] [1 1] [1 1] S₂ S₂ S₂ S₂ 011 4 10 7 1[1 1] [1 1] [1 1] [1 1] S₂ S₁ S₁ S₂ 100 2 8 5 11 [1 1] [1 1] [1 1] [1 1]S₂ S₁ S₂ S₁ 101 8 2 11 5 [1 −1] [1 −1] [1 −1] [1 −1] S₁ S₂ S₁ S₂ 110 104 1 7 [1 −1] [1 −1] [1 −1] [1 −1] S₁ S₂ S₂ S₁ 111 9 3 0 6 [1 1] [1 1] [1−1] [1 −1] S₂ S₂ S₂ S₂

The example shown in Table 5 corresponds to a method of mapping S₁ tofour of the 8 states of the DMRS_CS field and mapping S₂ to theremaining four states, as in the example shown in Table 4, andmaximizing MU-MIMO pairing capacity when the same OCC value is usedwhile reducing the minimum CS distance compared to the example of Table4.

That is, eight options (i.e. options e to 1) in Table 5 can maximize theminimum CS distance for N parameter sets and provide maximum CSorthogonality in cases to which the same OCC is applied (e.g. cases towhich [1, 1] is applied or cases to which [1 −1] is applied).

Option e is described as an example. When λ=0, λ=1, λ=2 and λ=3 are allconsidered, four cases to which OCC [1 1] is applied are present. Thatis, OCC [1 1] is applied to a case of the state 000 of the DMRS_CS fieldand λ=0, a case of the state 000 of the DMRS CS field and λ=1, a case ofthe state 111 and λ=0 and a case of the state 111 and λ=1. In other 12cases, OCC [1 −1] is applied. Here, the same n_(DMRS,λ) ⁽²⁾ value is notpermitted when the same OCC is applied. That is, different n_(DMRS,λ)⁽²⁾ values are respectively mapped to cases in which the same OCC isapplied. Since the example of Table 5 includes a case in which theminimum CS distance is 1, orthogonality may be decreased in terms of theminimum CS distance as compared to the example of Table 4. However, theexample of Table 5 can maximize multiplexing capacity since differentn_(DMRS,λ) ⁽²⁾ values can be applied to cases in which the same OCC isused all the time.

In options f to 1 in Table 5, a specific parameter set from among themultiple parameter sets can be indicated using the DMRS_CS field in theuplink-related DCI format and CS orthogonality can be maximized evenwhen the same parameter set is used and the same OCC is applied.

Table 6 shows another example with respect to the method for dynamicallysignaling a DMRS parameter set according to the present invention.

TABLE 6 n_(DMRS, λ) ⁽²⁾ [w^((λ))(0) w^((λ))(1)] Option DMRS_CS λ = 0 λ =1 λ = 2 λ = 3 λ = 0 λ = 1 λ = 2 λ = 3 m 000 0 6 3 9 [1 1] [1 1] [1 −1][1 −1] S₁ 001 6 0 9 3 [1 −1] [1 −1] [1 1] [1 1] S₁ 010 3 9 6 0 [1 −1] [1−1] [1 1] [1 1] S₁ 011 9 3 0 6 [1 1] [1 1] [1 −1] [1 −1] S₂ 100 0 6 3 9[1 1] [1 1] [1 −1] [1 −1] S₂ 101 6 0 9 3 [1 −1] [1 −1] [1 1] [1 1] S₂110 3 9 6 0 [1 −1] [1 −1] [1 1] [1 1] S₂ 111 9 3 0 6 [1 1] [1 1] [1 −1][1 −1] S₁

Table 6 corresponds to a modification of the conventional table (i.e.Table 2) that defines a mapping relationship between the DMRS_CS fieldand of n_(DMRS,λ) ⁽²⁾ and OCC (i.e. [w^((λ))(0) w^((λ))(1)]) and definesan implicit mapping relationship between state values of the DMRS_CSfield and DMRS sequence parameters.

For example, the mapping relationship with respect to only the states000, 001, 010 and 111 of the DMRS_CS field is defined in the same manneras the conventional mapping relationship (i.e. Table 2) and theremaining state values may be changed in Table 6. n_(DMRS,λ) ⁽²⁾ valuesand OCC values mapped to the states 000, 001, 010 and 111 of the DMRS_CSfield are equally mapped to the remaining states 011, 100, 101 and 110.Here, 000, 001, 010 and 111 are mapped to the first set S₁ and 011, 100,101 and 110 are mapped to the second S₂.

Accordingly, a specific parameter set from among a plurality ofparameter sets can be indicated using the DMRS_CS field in theuplink-related DCI format and the CS distance can be maximized when thesame parameter set is used to improve multiplexing capacity according toCS orthogonality in cases to which the same OCC is applied.

The aforementioned examples suggest various methods for maximizing theCS distance and/or CS orthogonality using of n_(DMRS,λ) ⁽²⁾ and OCC tobe applied to DMRS when a parameter set used for DMRS sequencegeneration is dynamically indicated. However, the scope of the presentinvention is not limited to the dynamic signaling method and one ofoptions a to m may be semi-statically set by a higher layer or only onethereof may be fixed. Alternatively, some options may be semi-staticallyset for a UE and one of the options may be dynamically signaled througha specific field (e.g. DMRS_CS field) of uplink-related DCI.

In addition, one of N parameter sets may include a parameter set (i.e.DMRS generation parameter set according to the conventional scheme,which is referred to as “PCI-included parameter set”) including a PCI(i.e. physical cell ID of a serving cell), cell-specific Δ_(ss) and/orcell-specific c_(init). For example, a specific set (e.g. S₁) from amongN parameter sets is always defined as the parameter including PCI andanother set (or other sets) may be defined as a VCI-included parameterset (or sets).

In this case, when N=2, the PCI-included parameter set and VCI-includedparameter set are defined and dynamic signaling (i.e. dynamic PCI/VCIswitching) may be applied therebetween. For example, S₁={PCI,cell-specific Δ_(ss), c_(init) used in the serving cell, etc.} can bedefined S₂={VCI₂, c_(init,2) ^(CSH)} can be set through higher layersignaling. Dynamic signaling/switching through a specific field ofuplink-related DCI, as described above, may be applied to the set {S₁,S₂}.

In addition, while the aforementioned examples of the present inventionsuggest the method of implicitly indicating a DMRS parameter set usingan existing field (e.g. DMRS_CS field) defined in uplink-related DCI,the DMRS parameter set may be explicitly indicated. That is, anadditional field for indicating a DMRS parameter set may be newlydefined in the uplink-related DCI.

In case of DCI format 0, the same bit width as that of DCI format 1A isset and a flag bit indicating 0/1A is included therein, and thus it isdifficult to define a new bit. Accordingly, an additional bit may bedefined in DCI format 4. Otherwise, a DCI format including the DMRSparameter set indication field suggested by the present invention may bedefined as a new DCI format X.

In addition, dynamic signalling of a DMRS parameter set may be performedusing only one of DCI formats 0 and 4. Otherwise, different numbers ofbits of the field for dynamic indication of a DMRS parameter set may beset for respective DCI formats. For example, the DMRS parameter setindication field may be defined as 1 bit in DCI format 1 and defined as2 bits in DCI format 4.

Here, the DMRS parameter set indication field is not limited to one ofthe method of implicitly indicating a DMRS parameter set using a statevalue of an existing field and the explicit indication method of addinga new field. In addition, while the DMRS_CS field is exemplified when anexisting field is reused, the DMRS parameter set indication field is notlimited to the DMRS_CS field and “Carrier Indicator” field, “TPC(Transmit Power Control) Command” field, “RAT(Resource Allocation Type)”field and the like may be used to indicate a DMRS parameter set.

For example, 1 bit indicating uplink multi-cluster resource allocationtype (RAT), which is included in fields defined in uplink-related DCI,may be reused (or implicitly indicated) as a dynamic DMRS parameter setindication bit. When carrier aggregation for configuring multiple cellsfor UEs is supported, resource utilization can be improved by permittingallocation of a non-contiguous frequency band to a UE located at thecenter of a cell. The RAT indication bit is used to indicate whetheruplink multi-cluster frequency allocation is applied. It may be assumedthat a UE, which operates according to the present invention for DMRSsequence generation when cooperative communication for multiple cells isperformed, is located at a cell edge and performs communication with aserving cell and a neighboring cell (or neighboring cells). Sincemulti-cluster uplink frequency allocation is not applied to the UElocated at a cell edge in most cases, it is expected that systemperformance is not deteriorated even when the RAT indication bit is usedfor other purposes.

To inform the UE that the RAT indication bit of the uplink-related DCIis reused as the DMRS parameter set indication bit for UL CoMP, the RATindication bit may be explicitly set by a higher layer (e.g. RRC). Inaddition, when the UE receives one or more VCIs for DMRS sequencegeneration through UE-specific higher layer signaling (in this case, theUE may operate in an operation mode in which a specific set from among aplurality of DMRS parameter sets is dynamically indicated through DCI),the UE may operate to interpret the RAT indication bit as the dynamicDMRS parameter set indication bit without additional signaling (i.e.implicitly). That is, when VCIs for DMRS sequence generation are setalthough the UE supports both contiguous uplink resource allocation andnon-contiguous uplink resource allocation, the UE can operate only inthe operation mode supporting contiguous uplink resource allocation.

Enhanced DMRS Cyclic Shift Index Determination Method

As described above with respect to Equation 11 and Tables 2 and 3, acyclic shift value for PUSCH in slot n_(s) is given asα_(λ)=2πn_(cs,λ)/12 and n_(cs,λ)=(n_(DMRS) ⁽¹⁾+n_(DMRS,λ)⁽²⁾+n_(PN)(n_(s)))mod 12 is defined. Here, n_(DMRS) ⁽¹⁾ iscell-specifically set through higher layer signaling (e.g. RRC message“PUSCH-ConfigCommon”) and is a parameter set through type-2 information(i.e. SIB2) of system information block (SIB). That is, n_(DMRS) ⁽¹⁾ iscommonly provided to UEs within one cell.

The present invention provides a method for setting the parametern_(DMRS) ⁽¹⁾ for using the conventional cell-specific cyclic shift indexper UE (or UE group) using UE-specific or UE group-specific higher layersignaling (e.g. UE-specific RRC signaling). Accordingly, DMRS sequencegeneration flexibility among UEs in the same cell can be improved. Thatis, while CS orthogonality between DMRS sequences of UEs is achievedonly when n_(DMRS) ⁽²⁾ is set as different values for UEs in the samecell since the same n_(DMRS) ⁽¹⁾ value is used for the UEs in theconventional scheme, the present invention can employ a method ofsetting one of n_(DMRS) ⁽¹⁾ and n_(DMRS) ⁽²⁾ to an identical value forthe UEs and setting the other to different values for the UEs or amethod of setting combinations of n_(DMRS) ⁽¹⁾ or n_(DMRS) ⁽²⁾differently to increase the number of cases in which orthogonality canbe provided between DMRS sequences.

Specifically, according to the method provided by the present invention,even when multiple UEs belonging to the same cell generate DMRSsequences using the same n_(DMRS) ⁽²⁾ value (value dynamically indicatedthrough uplink-related DCI (refer to Table 2)) in the same slot,different cyclic shift (CS) indices n_(cs,λ) may be determined for theUEs if different n_(DMRS) ⁽¹⁾ values (refer to Table 3) are respectivelyset for the UEs by a higher layer. Accordingly, DMRS sequence generationflexibility can be improved compared to the conventional scheme.

For example, UEs belonging to one cell may be classified into aplurality of groups and n_(DMRS) ⁽¹⁾ may be allocated per group.Accordingly, when UEs belonging to different groups are simultaneouslyscheduled, DMRS sequence orthogonality of each UE can be achieved sincethe simultaneously scheduled UEs use different n_(DMRS) ⁽¹⁾ values evenif the same n_(DMRS) ⁽²⁾ value is set for the UEs.

In addition, when different n_(DMRS) ⁽²⁾ values are applied to thesimultaneously scheduled UEs, n_(DMRS) ⁽¹⁾ may be UE-specifically orUE-group-specifically set to adjust a finally determined CS distance.For example, according to the conventional scheme with reference toTable 2, when the DMRS_CS field of the uplink-related DCI is set as 000for UE1 and thus n_(DMRS) ⁽²⁾ is determined as n_(DMRS) ⁽²⁾=0 and set as011 for UE2 and thus n_(DMRS) ⁽²⁾ is determined as n_(DMRS) ⁽²⁾=4 whenλ=0, the CS distance in DMRS sequences of the two UEs becomes 4. Sincethe conventional scheme is based on the assumption that the two UEs havethe same n_(DMRS) ⁽¹⁾ value, the finally determined CS distance ischanged when different n_(DMRS) ⁽¹⁾ values are set for the respectiveUEs. For example, when the same n_(DMRS) ⁽²⁾ value is set for the UEs asin the aforementioned example, the CS distance between the UEs can be 6(i.e. maximum CS distance) if n_(DMRS) ⁽¹⁾=0 is set for UE1 and n_(DMRS)⁽¹⁾=2 for UE2. The value n_(DMRS) ⁽¹⁾ may be set such that the CSdistance between the UEs decreases as necessary.

Accordingly, in DMRS sequence generation in UL CoMP operation of UEsbelonging to the same cell as well as UL CoMP operation of UEs belongingto different cells, CS indices are determined in consideration of theUE-specific value n_(DMRS) ⁽¹⁾ set (or pre-signaled) for UEs which areCoMP targets and the value n_(DMRS) ⁽²⁾ dynamically signaled throughuplink-related DCI at scheduling time and thus the CS distance can beefficiently set and DMRS orthogonality can be efficiently provided.

In addition, the present invention provides a dynamic signaling methodof setting one or more n_(DMRS) ⁽¹⁾ parameters (i.e. one or moren_(DMRS) ⁽¹⁾ parameter sets) through UE-specific or UE-group-specifichigher layer signaling and indicating a specific n_(DMRS) ⁽¹⁾ value fromamong the one or more n_(DMRS) ⁽¹⁾ parameters through uplink-relatedDCI.

To this end, state values of an existing field of the uplink-related DCImay be reused or n_(DMRS) ⁽¹⁾ may be implicitly indicated, or a newlyadded field may be defined to explicitly indicate n_(DMRS) ⁽¹⁾.

For example, some or all of 2 bits of the TPC command field included inthe uplink-related DCI may be used as an indication bit for indicatingn_(DMRS) ⁽¹⁾. However, the TPC command field is exemplary and the scopeof the present invention includes various schemes for using apredetermined field of the uplink-related DCI as the n_(DMRS) ⁽¹⁾indication bit.

In addition, one or more n_(DMRS) ⁽¹⁾ parameters set through UE-specificor UE-group-specific higher layer signaling may be set as a common valuefor all layers (or antenna ports, i.e. λ) of one UE or set as anindependent value per layer (or antenna port).

According to an additional suggestion of the present invention, the DMRScyclic shift index offset (i.e. Δn_(DMRS)) may be newly defined andused. For example, Δn_(DMRS) may have values of 0, 1, . . . , 11 and beset per UE (or UE group) through UE-specific or UE-group-specific higherlayer signaling. When Δn_(DMRS) is defined and used, the cell-specificparameter n_(DMRS) ⁽¹⁾ can be applied. Accordingly, an equation ofdetermining the DMRS sequence CS index can be defined as follows (thisequation can be regarded as a modification of the CS index equationdefined in the part above Table 3).n _(cs,λ)=(n _(DMRS) ⁽¹⁾ +Δn _(DMRS) +n _(DMRS,λ) ⁽²⁾ +n _(PN)(n_(s)))mod12  [Equation 32]

When DMRS sequence CS indices are determined according to Equation 32,the same n_(DMRS) ⁽¹⁾ value (refer to Table 3) is cell-specifically(i.e. UE-commonly) set for a plurality of UEs belonging to the same celland the UEs generate DMRS sequences using the same n_(DMRS) ⁽²⁾ value(value dynamically indicated through the uplink-related DCI (refer toTable 2)) in the same slot, cyclic shift index (CS index) valuesn_(cs,λ) of the UEs may be determined as different values if differentΔn_(DMRS) values are respectively set for the UEs. Provided Δn_(DMRS)=0in Equation 32, DMRS CS indices can be determined in the same manner asthe conventional method. Accordingly, DMRS sequence generationflexibility can be improved compared to the conventional method.

For example, UEs belonging to one cell can be divided into a pluralityof groups and Δn_(DMRS) can be allocated per group. Accordingly, whenUEs belonging to different groups are simultaneously scheduled, even ifthe same n_(DMRS) ⁽²⁾ value is set for the simultaneously scheduled UEs,DMRS sequence orthogonality of each UE can be achieved since the UEs usedifferent Δn_(DMRS) values.

Furthermore, even when different n_(DMRS) ⁽²⁾ values are applied to thesimultaneously scheduled UEs, a finally determined CS distance can becontrolled by setting Δn_(DMRS) UE-specifically orUE-group-specifically. For example, according to the conventional schemewith reference to Table 2, when the DMRS_CS field of the uplink-relatedDCI is set as 000 for UE1 and thus n_(DMRS) ⁽²⁾ is determined asn_(DMRS) ⁽²⁾=0 and set as 011 for UE2 and thus n_(DMRS) ⁽²⁾ isdetermined as n_(DMRS) ⁽²⁾=4 when λ=0, the CS distance in DMRS sequencesof the two UEs becomes 4. Since the conventional scheme is based on theassumption that the two UEs have the same n_(DMRS) ⁽¹⁾ value, thefinally determined CS distance is changed when different Δn_(DMRS)values are set for the respective UEs. For example, when the samen_(DMRS) ⁽²⁾ value is set for the UEs as in the aforementioned example,the CS distance between the UEs can be 6 (i.e. maximum CS distance) ifΔn_(DMRS)=0 is set for UE1 and Δn_(DMRS)=2 for UE2. The value Δn_(DMRS)may be set such that the CS distance between the UEs decreases asnecessary.

Accordingly, in DMRS sequence generation in UL CoMP operation of UEsbelonging to the same cell as well as UL CoMP operation of UEs belongingto different cells, CS indices are determined in consideration of theUE-specific value Δn_(DMRS) set (or pre-signaled) for UEs which are CoMPtargets and the value n_(DMRS) ⁽²⁾ dynamically signaled throughuplink-related DCI at scheduling time and thus the CS distance can beefficiently set and DMRS orthogonality can be efficiently provided.

In addition, the present invention provides a dynamic signaling methodof setting one or more Δn_(DMRS) parameters (i.e. one or more Δn_(DMRS)parameter sets) through UE-specific or UE-group-specific higher layersignaling and indicating a specific Δn_(DMRS) value from among the oneor more Δn_(DMRS) parameters through uplink-related DCI.

To this end, state values of an existing field of the uplink-related DCImay be reused or Δn_(DMRS) may be implicitly indicated, or a newly addedfield may be defined to explicitly indicate Δn_(DMRS).

For example, one or both of 2 bits of the TPC command field included inthe uplink-related DCI may be used as an indication bit for indicatingΔn_(DMRS). However, the TPC command field is exemplary and the scope ofthe present invention includes various schemes for using a predeterminedfield of the uplink-related DCI as the Δn_(DMRS) indication bit.

In addition, one or more Δn_(DMRS) parameters set through UE-specific orUE-group-specific higher layer signaling may be set as a common valuefor all layers (or antenna ports, i.e. λ) of one UE or set as anindependent value per layer (or antenna port).

While operations capable of efficiently supporting CoMP operation usingan uplink DMRS have been described above, the scope of the presentinvention is not limited thereto and the principle of the presentinvention can be equally applied to other uplink RStransmission/reception schemes.

FIG. 13 is a flowchart illustrating a method for transmitting an uplinkDMRS according to an embodiment of the present invention.

A UE may be provided with one or more parameter set candidates for PUSCHDMRS sequence generation from a BS through higher layer signaling (e.g.RRC signaling) in step S1310. A parameter set may include one or more ofa VCI used for DMRS generation, an offset parameter Δ_(ss) between aPUCCH DMRS sequence shift pattern and a PUSCH DMRS sequence shiftpattern, an initial value c_(init) ^(CSH) of a pseudo-random sequencefor determining a DMRS CSH pattern, a first parameter n_(DMRS) ⁽¹⁾ forDMRS CS index determination, a second parameter n_(DMRS) ⁽²⁾ for DMRS CSindex determination and a CS index determination offset Δn_(DMRS).

The UE may receive information indicating a specific parameter set fromamong the parameter set candidates through uplink-related DCI from theBS in step S1320. To this end, a DMRS CS and OCC indication field, RATindication field, TPC indication field or the like of the uplink-relatedDCI may be used.

The UE may generate a DMRS using the specific parameter set and transmitthe DMRS to the BS in step S1330. The position of a resource element towhich the DMRS is mapped is as described above with reference to FIGS. 5to 10.

When the BS receives an uplink reference signal transmitted from the UE,the BS may detect the reference signal on the basis of the assumptionthat the UE has generated the reference signal according to thereference signal sequence generation method provided by the presentinvention.

The aforementioned various embodiments of the present invention may beindependently applied or two or more thereof may be simultaneouslyapplied and description of redundant parts is omitted for clarity.

FIG. 14 illustrates a configuration of a UE according to a preferredembodiment of the present invention.

Referring to FIG. 14, a UE 10 may include a transmitter 11, a receiver12, a processor 13, a memory 14 and a plurality of antennas 15. That aplurality of antennas is used means that the UE supports MIMOtransmission and reception. The transmitter 11 may transmit signals,data and information to an external device (e.g. BS). The receiver 12may receive signals, data and information from an external device (e.g.BS). The processor 13 may control overall operation of the UE 10.

The UE 10 according to an embodiment of the present invention may beconfigured to transmit an uplink signal.

The processor of the UE 10 may receive a VCI (e.g. n_(ID) ^(RS)) from aBS through higher layer signaling (e.g. RRC signaling) using thereceiver 11. Here, a VCI (e.g. n_(ID) ^(PUSCH)) for a PUSCH DMRS and aVCI (e.g. n_(ID) ^(PUCCH)) for a PUCCH DMRS may be independentlysignaled/set.

The processor 13 of the UE 10 may be configured to generate a referencesignal sequence (e.g. PUCCH DMRS sequence and/or PUSCH DMRS sequence).The embodiments of the present invention may be applied to DMRS sequencegeneration. For example, when the VCI is set by a higher layer, theprocessor 13 may determine a group hopping pattern, a sequence shiftpattern, a sequence hopping value and/or CS hopping value and the likeaccording to the embodiments of the present invention and generate aDMRS sequence using the determined values. Alternatively, theembodiments may be implemented in such a manner that group hoppingpatterns, sequence shift patterns, sequence hopping values and/or CShopping values for available values of the VCI are pre-generated andstored in a table and appropriate values are detected according to a setVCI value. When the VCI is not set by the higher layer, the PUCCH DMRSsequence and/or the PUSCH DMRS sequence may be generated using a PCI asdefined in the conventional wireless communication system.

In addition, the processor 13 of the UE 10 may be provided with one ormore parameter set candidates used for PUSCH DMRS sequence generationthrough higher layer signaling and receive information on indication ofa specific parameter set through uplink-related DCI. Accordingly, thePUSCH DMRS sequence can be generated using the specific parameter set.

The processor 13 of the UE device 10 can map the generated DMRS sequenceto an uplink resource and transmit the DMRS sequence to the eNB usingthe transmitter 12. The positions of REs mapped to the PUSCH DMRSsequence and the positions of REs mapped to the PUCCH DMRS sequence areas described with reference to FIGS. 5 to 10.

In addition, the processor 13 of the UE device 10 processes informationreceived by the UE device 10, information to be transmitted to anexternal device, etc. The memory 14 can store the processed informationfor a predetermined time and can be replaced by a component such as abuffer (not shown).

The UE device 10 may be implemented such that the above-describedembodiments of the present invention can be independently applied or twoor more embodiments can be simultaneously applied, and redundantdescriptions are avoided for clarity.

An eNB device according to an embodiment of the present invention caninclude a transmitter, a receiver, a processor, a memory and antennas.When the processor of the eNB device receives an uplink RS transmittedfrom the UE device 10, the processor of the eNB device can be configuredto detect the uplink RS on the assumption that the UE device 10generates the uplink RS according to the RS sequence generation schemeproposed by the present invention.

While an eNB is exemplified as a downlink transmission entity or anuplink reception entity and a UE is exemplified as a downlink receptionentity or an uplink transmission entity in the embodiments of thepresent invention, the scope of the present invention is not limitedthereto. For example, description of the eNB can be equally applied to acase in which a cell, an antenna port, an antenna port group, an RRH, atransmission point, a reception point, an access point or a relay nodeserves as an entity of downlink transmission to a UE or an entity ofuplink reception from the UE. Furthermore, the principle of the presentinvention described through the various embodiment of the presentinvention can be equally applied to a case in which a relay node servesas an entity of downlink transmission to a UE or an entity of uplinkreception from the UE or a case in which a relay node serves as anentity of uplink transmission to an eNB or an entity of downlinkreception from the eNB.

The embodiments of the present invention may be implemented by variousmeans, for example, hardware, firmware, software, or combinationsthereof

When the embodiments of the present invention are implemented usinghardware, the embodiments may be implemented using at least one ofApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

It is obvious to those skilled in the art that claims that are notexplicitly cited in each other in the appended claims may be presentedin combination as an exemplary embodiment of the present invention orincluded as a new claim by subsequent amendment after the application isfiled.

INDUSTRIAL APPLICABILITY

The above-described embodiments of the present invention can be appliedto various mobile communication systems.

The invention claimed is:
 1. A method of transmitting, by a userequipment (UE), an uplink signal in a wireless access system, the methodcomprising: receiving configuration information regarding a plurality ofparameter set candidates related to a reference signal for demodulationof a physical uplink shared channel (PUSCH); receiving downlink controlinformation (DCI) including a predetermined field set to a specificindex from among a plurality of indices, the specific index indicating aspecific cyclic shift (CS) set from among a plurality of CS sets, aspecific orthogonal cover code (OCC) set from among a plurality of OCCsets and a specific parameter set from among the plurality of parameterset candidates; generating a sequence of the reference signal using thespecific CS set, the specific OCC set and the specific parameter set andtransmitting the generated reference signal sequence to a base station(BS), wherein the plurality of parameter set candidates have a mappingrelation to the plurality of CS sets and the plurality of OCC sets suchthat a minimum distance between CS parameters for a layer in CS sets towhich a same parameter set candidate among the plurality of parameterset candidates is mapped is maximized, and wherein the specificparameter set includes information on each of: a virtual cell ID (VCI)used for the generation of the reference signal sequence, an offsetparameter Δ_(ss) between a sequence shift pattern of a physical uplinkcontrol channel (PUCCH) demodulation reference signal (DMRS) and asequence shift pattern of the PUSCH DMRS, an initial value c_(init)^(CSH) of a pseudo-random sequence which determines a cyclic shifthopping pattern of the PUSCH DMRS, a first CS parameter n_(DMRS) ⁽¹⁾used to determine a CS index for the reference signal, and an offsetΔn_(DMRS) used to determine the CS index.
 2. The method according toclaim 1, wherein the predetermined field is a demodulation referencesignal (DMRS) cyclic shift (CS) and orthogonal cover code (OCC) field.3. The method according to claim 1, wherein whether the predeterminedfield indicates the specific parameter set is configured by a higherlayer.
 4. The method according to claim 1, wherein the informationregarding the plurality of parameter set candidates is UE-specificallyor UE-group-specifically signaled by a higher layer.
 5. The methodaccording to claim 1, wherein the specific parameter set isindependently configured per layer of the UE.
 6. The method according toclaim 1, wherein the UE is paired with another UE for multiple user MIMO(MU-MIMO).
 7. The method according to claim 1, wherein the referencesignal is transmitted on one SC-FDMA (single carrier frequency divisionmultiple access) symbol in a slot in which the PUSCH is transmitted. 8.A user equipment (UE) of transmitting an uplink signal, comprising: areceiver; a transmitter; and a processor configured to: receiveconfiguration information regarding a plurality of parameter setcandidates related to a reference signal for demodulation of a physicaluplink shared channel (PUSCH) via the receiver, receive downlink controlinformation (DCI) including a predetermined field set to a specificindex from among a plurality of indices, the specific index indicating aspecific cyclic shift (CS) set from among a plurality of CS sets, aspecific orthogonal cover code (OCC) set from among a plurality of OCCsets and a specific parameter set from among the plurality of parameterset candidates via the receiver, generate a sequence of the referencesignal using the specific CS set, the specific OCC set and the specificparameter set, and transmit the generated reference signal sequence to aBS via the transmitter, wherein the plurality of parameter setcandidates have a mapping relation to the plurality of CS sets and theplurality of OCC sets such that a minimum distance between CS parametersfor a layer in CS sets to which a same parameter set candidate among theplurality of parameter set candidates is mapped is maximized, andwherein the specific parameter set includes information on each of: avirtual cell ID (VCI) used for the generation of the reference signalsequence, an offset parameter Δ_(ss) between a sequence shift pattern ofa physical uplink control channel (PUCCH) demodulation reference signal(DMRS) and a sequence shift pattern of the PUSCH DMRS, an initial valuec_(init) ^(CSH) of a pseudo-random sequence which determines a cyclicshift hopping pattern of the PUSCH DMRS, a first CS parameter n_(DMRS)⁽¹⁾ used to determine a CS index for the reference signal, and an offsetΔn_(DMRS) used to determine the CS index.
 9. The method according toclaim 1, wherein each of the plurality of OCC sets includes OCCs appliedto the reference signal for up to 4 layers.
 10. The method according toclaim 1, wherein each of the plurality of CS sets includes second CSparameters for up to 4 layers used for determining the CS value for thereference signal.
 11. The user equipment according to claim 8, whereinthe predetermined field is a demodulation reference signal (DMRS) cyclicshift (CS) and orthogonal cover code (OCC) field.
 12. The user equipmentaccording to claim 8, wherein whether the predetermined field indicatesthe specific parameter set is configured by a higher layer.
 13. The userequipment according to claim 8, wherein the information regarding theplurality of parameter set candidates is UE-specifically orUE-group-specifically signaled by a higher layer.
 14. The user equipmentaccording to claim 8, wherein the specific parameter set isindependently configured per layer of the UE.
 15. The user equipmentaccording to claim 8, wherein the UE is paired with another UE formultiple user MIMO (MU-MIMO).
 16. The user equipment according to claim8, wherein the reference signal is transmitted on one SC-FDMA (singlecarrier frequency division multiple access) symbol in a slot in whichthe PUSCH is transmitted.
 17. The user equipment according to claim 8,wherein each of the plurality of OCC sets includes OCCs applied to thereference signal for up to 4 layers.
 18. The user equipment according toclaim 8, wherein each of the plurality of CS sets includes second CSparameters for up to 4 layers used for determining the CS value for thereference signal.